I agree with those who think images two and four are from the Zeiss, though second-guessing the focusing differences makes things tricky. I mostly used the eyebrows to estimate sharpness, since the in-focus area seems to land somewhere on the eyebrows in most images.
The Nikkor 105 mm f/2.5 AIS is an amazing lens that I very much enjoy owning. Its legendary reputation is well-deserved. The old photodo website showed basically identical performance to the Canon EF 135 mm f/2 L both at full aperture (albeit at two-thirds of a stop slower) and f/8. Of course the Nikkor is far better made, smaller, and far cheaper.
Still, the Zeiss Planar should show its pedigree in terms of sheer sharpness at very large apertures and very close focusing distances.
Images with entirely blurred, featureless backgrounds with no specular highlights—like Todd's photos here—make bokeh differences practically invisible (and both these lenses have good bokeh, though with a few rendering differences). Likewise, shooting under an overcast sky will reveal differences in flare performance that typical studio lighting will minimise. The Zeiss might be much more contrasty under a bright sky.