I had the opportunity to play with Z 50 yesterday and the overall impression is very good
Small, light and capable and the 16-50 lens is a good performer for a camera that can be almost always with me
I checked some f mound lenses with FTZ- 35 dx, 50, 85 all f1.8 with not much significance IQ difference except 85
I also check AF-S 300/4 but I noticed some delay or not focus sometimes
The same lens is working with no issues on my D750
Tamron 150-600 no G2 as expected was only manual focus and also Tamron 70-200 2.8 G2 after firmware update was OK
Do you have similar issues with autofocus in lens you checked or not?
By the way Z50 in such a big lens is not a good idea you need something bigger to handle better
After holding Z 50 with kit lens, D750 with its kit 24-105 looks like a monster, almost 3X on weight
Thank you