Hi Gil,
And welcome to UHH!
A mistake a lot of people make with tripods is not spending enough. A good quality tripod can last a lifetime. One of mine is 40 years old, but I got older and heavier than I liked to carry in the field. So 20 years ago I got another that weighs about half as much, still does great holding any camera or lens I wish and I leave the heavy one "in studio".... though I don't currently have a studio so it's actually in storage.
You didn't mention a budget, but that did tell us what you want to put on it and that you primarily want to use it out in the field shooting wildlife. Based on that I can make some general recommendations and leave it to you to decide what you're comfortable spending.
Your camera and lens probably weigh about 7 or 8 lb. I'd recommend a tripod and head rated to support about 3X that weight, at a minimum. (Weight ratings aren't ideal as a means of judging stability... But that's the info we usually have for comparison purposes.)
Next I would recommend light weight... but not too light. Carbon fiber typically costs more, but saves weight. It's also durable and absorbs fine vibrations better than metal.
Look for a tripod that has as few leg sections as possible. Three sections is about as few as is practical for most people, but I wouldn't recommend more than four section legs. More than that and the lowest sections get really slim to fit inside the section above, plus there are those additional joints that might flex.
A tripod that's tall enough for you without any center column would be ideal. However, most have a center column. Look for one that's tall enough without having to raise the center column much or at all. Measure your eyeline and add an inch or two to figure out how tall a tripod you need to be comfortable using it (the camera itself sitting atop the tripod will add a couple more inches). It ain't much fun shooting with a tripod you always have to bend over tor use! Finally, when shopping do a lot of research about the actual height of the tripods you're considering. Some only give a height with the center column fully extended (again, that's not good). Look for info about the height "without column extended", as shown on some sites.
Look for a "kit" that best meets your needs, if at all possible. It's possible to buy just the legs and then fit your choice of head... but that is typically more expensive. Hopefully you can save a little with a kit that does all you need. Another possible advantage... the height of a kit will probably be measured to the platform of the head, accounting for both the legs and the head. When bought separately, you need to try to figure out the total height yourself, based upon the dimensions of the separate parts.
There are a variety of types of tripods, as well as "special features" offered. For example, "travel" tripods emphasize lighter weight and are designed to fold up as compact as possible. Many of them have legs that fold in reverse, back over the head. Because of this they usually only use ballheads and are limited the size of head that can be fitted. A different type of head or too large a ballhead will prevent the legs from reverse folding, as intended. Some travel tripods also have lots of leg sections (see above) or extra long center columns that may make them slower to set up and less stable. I'm also a bit skeptical about some features such as center columns that rotate to the horizontal or beyond or legs that can be removed to make a monopod. Do those "features" make the tripod less stable or create a potential failure point? Are they really necessary? Some tripods can go really low without rotating the center column to horizontal. Any tripod that's not too heavy can be used like a monopod, simply by not spreading the legs and only extending one of them.
Choose what type head you want. At least initially I would recommend a ballhead for most people hiking around looking for wildlife to photograph. Ballheads typically have the best weight to strength ratio, plus don't have protruding handles that might catch on branches or whatever, and allow the rig to be the most compact. Working with a large telephoto lens like a 150-600mm and shooting active wildlife, you might want a gimbal head. But that's something you can add later (see below).
Gimbal heads are quite popular with sports and wildlife photographers. They can be set "loose" for either tilt or panning axis, or both, to allow you to follow moving subjects smoothly. In addition, set up correctly they make manipulating larger, heavier telephotos fairly easy. With proper equilibrium I can swing around 15 lb. of lens, camera, flash and accessories with one finger. There are a couple different types of gimbal heads: full size that replace any other head on the tripod (making it "large telephoto only") or gimbal "adapters" that work in conjunction with a ballhead on the tripod. I use both types personally. I use the tripod with a ballhead and a gimbal adapter most often because that tripod can also serve with shorter lenses when needed, without need to swap the heads. My other tripod with the full size gimbal head is dedicated for use only with large telephotos that have a built in tripod mounting collar. There is no way to comfortably use a camera with a shorter lens on it, unless I remove the gimbal and install a different head... which is a pain, means carrying around both heads and possibly tools to make the swap.
There are various types of leg locking mechanisms, too. On a tripod I'll be carrying around in the field I prefer the twist type because they're low profile to reduce chance of catching or a branch or a sleeve, self-adjusting for wear and somewhat resistant getting dirt and water inside (some even have seals). Twist type may not be quite as quick to set up as lever type, but the levers protrude to catch on branches and such, are prone to wear over time and may need adjustment or fail. Also dirt might get in them and effect their function (granted, in worst case situation dirt can get into some of the twist type, too). Third type of locks are thumb screws. They are reliable and don't have wear issues, but protrude and are the slowest type to set up.
Twist type leg logs are only used with tubular legs. When they are plain round tubes, one section might rotate while you are trying to tighten another. You need to learn to work from the largest diameter to the smallest when loosening or tightening them. But many newer tripods have some sort of anti-rotation design to prevent this and make it even easier to use the twist type locks. It's something to look for when you're comparing tripods.
Levers and thumbscrews are used on tubular legs too, but also are sometimes used on legs with a different shape in cross section... rectangular, for example. However, these are typically only found in the cheapest and flimsiest tripods, which you'd be wise to avoid. They simply don't work very well, aren't much fun to use and usually fail in relatively short time.
An option you'll see on all types of tripod heads are quick release (QR) systems. Unless you are using a gimbal, you don't need to use these. All cameras and lenses have a 1/4" socket that fits the same size screw on virtually all tripod heads. However, if you use a gimbal head or adapter a QR system is essential and nearly all of those use one particular type (more about that below). All QR systems require plates fitted to the bottom of your lens(es) and camera that lock into a platform on top of the tripod head. By far the most common and universal of these is the Arca-Swiss system, which is used by many different manufacturers and is very largely interchangeable across brands. There are others that are "proprietary"... exclusive, patented designs used by particular brands. One of the most popular brands... Manfrotto... uses not one, but three different QR systems (which aren't even compatible with each other). At least the proprietary QR Manfrotto uses are common enough that parts are usually available. That's not the case with some other brands. They can be difficult to get additional plates or replacement parts if needed.
I fully switched to the Arca system around 20 years ago when I started using gimbals, since they pretty much require it. The gimbal adapter I use and all the ones I'm aware of only work with a tripod head fitted with an Arca style platform. Nearly all full size gimbals also use it, because the design allows some adjustments that are needed for best equilibrium with big, heavy gear. If I had known up front and bought into the Arca system from the start, it would have saved me quite a bit of $ wasted on other systems and later having to buy converters or replacement parts. There are dozens of manufacturers making components for the Arca QR system. These include specialized parts such as fitted camera and lens plates. In fact, some lens makers and even one or two camera makers are incorporating an Arca compatible dovetail into their gear, so that additional parts aren't even needed. For example, there are camera plates specifically made to fit your Z9II. These have an anti-twist feature that's important (a feature many "generic" plates lack). If your 150-600mm is a Tamron G2 it will have an Arca dovetail built right into the foot of the tripod mounting ring. A recent Sigma lens might have this, too.
A popular accessory if using the Arca system is an L-bracket to fit the camera (instead of a camera plate). An L-bracket provides two ways of attaching the camera to the head, when not using a long lens with a built-in tripod mounting ring. A camera plate is more compact and fitted to the bottom of the camera will work fine on any type of head with a compatible platform when the camera is in the horizontal/landscape orientation. While the vast majority of tripod heads can be rotated to orient the camera to the vertical/portrait orientation, particularly with ballheads this puts the weight off to one side and that can be less than ideal. The L-bracket makes for more stability by keeping the camera directly above the head in either orientation. No need to "flop" the head off to one side (and possibly have the tripod, camera, lens and all fall over to one side!) An L-bracket does add cost and bulk to the camera. L-brackets also pretty much need to be a custom design fitted to each camera model, so that all the controls, sockets, battery and memory card compartments, etc. can easily be accessed. An L-bracket can be added later, if wanted.
With both camera plates and L-brackets, if you use a battery grip on your camera it will usually us a different one than if it doesn't have a grip installed. So be careful to get the correct one for however your camera is set up.
A few other things may be nice to have, but also can be added later if necessary. For example, you might want a bag with a strap to carry, protect and store the tripod. Some kits include that, but if not they are also available to buy separately. Another handy thing is padding on at least one of the legs, to be more comfortable carrying the tripod over your shoulder. Some tripods have that padding, but it's also possible to add if the tripod you select doesn't. Another thing that can be helpful with a gimbal head is a leveling platform that fits between the head and the tripod legs. Those are only sold separately and add about 1 lb. of weight, but also add in inch or two of height and can make setups faster when using a gimbal. Gimbals work best when things are reasonably level, which can be achieved by adjusting the leg lengths individually. A leveling platform just speeds up the process (and possibly makes it safer for your gear), but it can add up because re-leveling might be necessary every time you move the tripod on uneven ground.
The big online photography stores such as Adorama and B&H Photo have a lot of info and tools that can be helpful when shopping for a tripod. For example, I did a quick search at the B&H website for a tripod w/ballhead rated for 22 to 44 lb., with carbon fiber legs, twist type legs locks and Arca-Swiss QR compatibility. B&H lists over 1000 tripods, but this search criteria quickly reduces the number to 68. You might be able to reduce this even further, for example there are just 9 of those tripods that don't have a center column. You also can limit by price, the current range is pretty wide: $136 to $1550. (I might be suspicious of the least expensive!) Also study or filter for the number of leg sections and height. If there are still several to choose, I'd lean toward the one with the heaviest rating and the most well known, long-established brand.
Here's a link to the search I did at B&H:
https://www.bhphotovideo.com/c/products/Complete-Tripods-with-Heads/ci/2635/N/4075788742?sort=PRICE_LOW_TO_HIGH&filters=fct_head-type_4106%3Aball-head%2Cfct_leg-lock-type_4128%3Atwist-lock%2Cfct_material_774%3Acarbon-fiber%2Cfct_quick-release-system_7375%3Aarca%2Cfct_support-weight_4142%3A22-lb%7C24-lb%7C25-lb%7C26-lb%7C27-lb%7C28-lb%7C30-lb%7C31-lb%7C33-lb%7C34-lb%7C35-lb%7C39-lb%7C40-lb%7C44-lbFinally, try to buy from a store that allows easy returns, just in case you make a mistake and find yourself with a tripod that doesn't meet all your expectations.
Have fun shopping!