If you already have the lens, it may be worth purchasing an FTZ. If you are looking at purchasing the lens, I would recommend looking very hard at a Z mount lens. IMO, it's worth spending the extra on the Z mount lenses, they really are a cut above. Having said that, there are situations where the comparable Z mount is a lot more than an F mount and the adapter. I don't regret getting the 200-500 F5.6 for my Z5. At the time, there were no long telephotos available in Z mount for less than about $2800. If I were buying now, I wouldn't hesitate to spend the extra for the Z 180-600.
FYI, the Z 24-120 F4 runs $1100 and is a constant aperture S line lens. The S line lenses are weather sealed, and generally better quality than standard lenses. I have no doubt you would be much happier with this lens, assuming you can afford to spend the extra on it. The lack of autofocus would be a deal killer for most folks these days, unless it is a specialty lens.