I think I finally figured out what's going on with the varied comparisons between these lenses.
1) the Nikon suffers from focus shift, making testing iffy
2) the Zeiss has field curvature in the corners (towards near), great for foreground, lousy if there happens to be something at distance in the corner, almost the opposite of the Nikon
3) the Zeiss is sharper than the Nikon over most of the field.
4) the Nikon is sharper in the corners (see 2) above)
In theory live view would fix the focus shift but there is so much depth of field that one would need to open up and adjust the exposure, both inconvenient and negating the workaround for the focus shift. The Zeiss doesn't shift and can be focused in the viewfinder - I haven't tried live view with it yet but no doubt it too will have the same problems focusing stopped down.