There are charts all over the internet stating which lenses work and which dont work with the FTZ adapter. The Tamron lens I have is the V1. They (Nikon) killed off the V1 lenses for use on the mirrorless system so they (Tamron) came out with the V2. You need the V2, the one with the ability to update via the tap in console to use properly with the FTZ (autofocus). My Tamron 85mm 1.8 works as it should, it has the ability to receive updates via the tap in console. I have 2 Tokina lenses, and both are spectacular. The problem lies with the FTZ adapter and or the firmware. My Tokina 100mm is screwdrive, therefore is manual focus only (still awesome to use on the Z because of the focus peaking and added in body stabilization, albeit sans AF due to the lack of a pass through drive gear that should have been included in the FTZ adapter). The 11-16 gets automatically cropped and that was a bit of a shock to me. With the Z6 camera, that lens is essentially useless to me now. I didnt see anywhere in the past year in looking into the Z's the crop was automatic. I assumed it was the same as my only other full frame camera where you could choose to force it to shoot full frame with a crop lens, showing the crops vignette if the image circle wasnt big enough, but there are many lenses including zooms where the end of the zoom, the image circle is not cropped. I really wanted to use that for my wide lens since its small, light weight and compliments the feel of the Z, the 24-70 F4 and 70-300. On FX, it's a 16mm f2.8 prime, but not with the auto crop. The Tokina 16-28 is a beast of a lens, just as big as the Tamron but without stabilization, which is why I chose the Tamron when I did. Bottom line, everything has plusses and minuses. If I had this issue in the Z7, I could live with it since DX crop is still 20mp, but 10mp on the z6? Not gonna happen. Not complaining, was just unaware of the limitations of a specific need. I am overall very happy with the Z6.
EDIT:
Just tried the Tamron again and it works better than the first try. It will autofocus with limitations. I upgraded to the latest firmware just released for the Z6 after trying the AF compatibility the first time but I don't know if that's what helped or if I was just in the wrong settings to get the right results the first time. I've run some tests around the house and in my experience, the Tamron 15-30 SP V1 will AF as long as the pick box is small. Pin point is best followed by single point. I tried wide small and that works too if the subject is big enough. As the pick box increases in size, its given too many choices to focus on and goes on a MAJOR hunting frenzy, racking back and forth and even doing some electrical buzzing and flashing the ISO 4-5 stops higher than normal. If gone on too long, the camera throws a message on the screen, Error- press shutter release button. The shutter button resets the error and you are able to try again. Not ideal, not too bad either. I can always manual focus with it too. It'll be a good band aid until I come up with a better solution.