Have you tried the full frame lenses - in particular the 85mm?
Maybe someone can give you more help
I had the chance to try the viltrox 85 1.8 lens on Z6 last Friday in an photo exhibition and it was very good overall
It’s quite bulk, I only got Nikon 1.8G to compare, more contrasty than mine a little out of Nikons typical colors
I used eye af and noticed a bit out of focus on some snapshots not perfectly on the eye, I don’t know may be needed some kind of firmware update it was an out of the box copy
I’ll probably go for it if I had no 85 in my bag