Even DXO couldn’t find much in the way of improvement from Nikon’s Z6 24 megapixel sensor to the new version in its Mark II upgrade of the same camera.
Both the Nikon Z6 and the Nikon Z7 appear to have been mostly rebadged, rather than upgraded, although there were some non-image-path improvements, such as the addition of another card slot, and more processing power to provide more file cooking.