The Vltrox lenses are really good. Not perfect, but great value for their rather modest selling price. The added bonus is they are small and neat, a description one would never use for the equivalent Z Nikkors
The beefy Z9 and the small lens makes for excellent handling of the combo. My suspicion is that the AF speed of the Viltrox is enhanced on the Z9, compared to the Z fc for which I purchased them in the first place.
Viltrox just released a 13mm f/1.4 AF for the Fuji system and I'm eagerly awaiting its likely future launch as a Z lens.
Of course having a DX lens on the FX Z9 shrinks the file size substantially, but there are still plenty of pixels left.