The Nikon D850 and the Z7II both have the same sized sensor - and supposedly different versions of the same sensor. In comparing Uncompressed 14 bit RAW files from the two cameras, the Z7II file is roughly 13% smaller - averaging 84 MB compared to 97 MB for the D850 image. The pixel dimensions of both cameras are the same. I've verified I am selecting the correct settings in the camera, but that does not mean Uncompressed files are the same. File size for 8-10 sample images varied less than 0.5%. I tested with a range of ISO settings including base ISO 64 for both cameras.
I can provide RAW files for comparison.
RawDigger does not fully support the Z7II yet, but I'm new and might have missed something.