A quick update to my post from yesterday – one of my sources sent me this comparison of the Nikon Z8 camera size with the Z7, Z9, and D850:
Also, in the previous Nikon Z8 mockup I posted last year, the camera in the background is the Z9 – it also gives a perspective on how big the Z8 is rumored to be:
The Nikon Z8 is rumored to be approximately the same size as the Nikon D850 (just slimmer)