That's interesting. What lenses would you like to have other than 85mm f/1.2 which doesn't exist on Sony?
I get a feeling that Nikon bodies are both very nice minus the EVF and good value for what they can do. You really need to go all the way to Sony A1 to match or exceed it.
Meanwhile, there is a much greater variety of E mount lenses, everything from more affordable to ultra premium options including great value high performances designs like Sigma ARTS, or this new Viltrox thing. These also have faster linear motors. I'm not sure what Z mount STM motor is like, but they are not very likeable in Canon's budget lenses or Sigma 70mm.
You can at least in theory adapt E to Z but I wonder if you run into issues like AF, let alone profiles not working until the software stage. That is kind of important shooting video at wide apertures for example.
I really expected more Z lens choice at this point. Canon is no better, maybe worse unless you come with a bag-full of EF mount ART lenses, which does give a substantial incentive for R5II.