Thank you very much everyone!
I'm choosing to buy both the 150mm 2.8 and Macro 120mm because they both serve different purposes, the 150mm gives you shallow depth of field and it's less sharp, specially wide open. And the 120mm macro is super sharp. You can use it on male clients. And the 150mm on females.
I would like to go with AF lenses, because I have a hard time focusing manual on the 645D. Unless I'm on a tripod and the subject doesn't move at all, but specially wide open, you'll get around 2-3 inches in depth of field on a headshot, if the subject moves a little bit you can miss focus and judging focus on 40-50MP on such a small viewfinder is hard
I don't own or have even used a FF 35mm DSLR, all I have are two APS-C cameras, both with autofocus(Canon T1i and Fuji X100). So I don't know how is the manual focus on an optical viewfinder in that sensor size. Maybe using live view on the 645Z or on the Nikon 850 is a good way to judge focus. But I don't have that on the 645D, so don't know.
Although I haven't used a Zeiss still lens, other than the old Hassy V lenses. I have used them in numerous ocasiona in cinematography, the last film I shot I use vintage Zeiss High Speeds(T1.3). Stills from that film, taken from the footage.
Las Reglas Del Rey Stills | Flickr
I loved those Zeiss High Speed, they're incredible with high resolution digital cinema cameras. But in cinematography it's different, you want lenses with more character, new Zeiss lenses are too sharp for most of what I shoot. I prefer Cooke S4 lenses. But I have used the Zeiss Ultra Prime and Master Primes on many occasions. But I'll definitely test the new Zeiss still lenses if I get the Nikon.
I know the K1, is excellent and every bit as good as the Nikon 810, in picture quality. But the only reason to move away from Medium format is because of ease of use and compatibility. I hate having to look for ways to use HSS, and use something like cam ranger, or even work thetered. And most solutions and pretty cumbersome or expensive.
That's the only reason I would use a FF 35mm DSLR for convenience. And I would chose Nikon for IQ over a Canon.
I have three months to make a decision, I'm getting paid a TV series I'm shooting right now, and I'll buy it with part of that.
PS: I tested the Fuji GFX, and it's a great camera, but it's more expensive, and I would have to sell my 645D and lenses to buy the body and 1 lens or maybe two. And I don't know how much improvement there will be from a 645Z which will be cheaper for me.
Thanks again, and if you have some more suggestions or comments, please leave them.