I was able to check out the Z series cameras at the recent Nikon Pro Event:
I did tests with the Z7, FTZ adaptor and both the Nikkor 8-15mm f/3.5-4.5 and the 105mm f/2.8 VR lenses
"I was able to use the Z7 with both the Nikkor 8-15mm f/3.5-4.5 fisheye and the 105mm f/2.8 VR macro lenses. Both required the use of the ZTF adaptor. Predictably, the AF seems fine with the fisheye. I then mounted the 105mm and I was disappointed with the results. While it found focus on a brightly lit subject, it hunted a lot to do so. Certainly, when compared with the amazing AF on the D500/D850/D5, the Z7’s felt both slower and less accurate."
I'm quite sure the Z series cameras are amazing, but I would suggest that there are significant compromises in lens choices at present. Saying that Nikonos conversions may well produce amazing results...