No, the two tools are different in fundamental ways. The FTZ adapter exists to place the lens to the proper F-mount flange distance using the Z-mount. The difference is 30.5mm, where the legacy F-mount is 46.5mm and the new Z-mount is 16mm. Without the FTZ adapter setting the proper distance to 46.5mm, the F-mount lenses could not focus onto the mirrorless sensor.

Extension tubes move the lens even further from the film / sensor. This change (further away) lets the lens focus on closer subjects by changing the minimum focal distance of the lens. But at the same time, the lens can no longer focus to infinity (anything distant) with the extension tube installed.