First off, the comparisons are to evaluate potential lens candidates for my D800. I didn't feel as though my 10-year-old 17-35mm was up to par. Thus, I rented the Nikkor 14-24mm and Zeiss 21mm to begin evaluation against my 17-35mm. And, yes, your point is well taken with respect to rental equipment. Once I narrow my selection, I will only purchase where I can try multiple copies, either through an in person purchase or a no quibble 14 to 30 day return policy. As we know, not all lenses are equal.
I thought I may as well include the Hasselblad in the comparison as a benchmark as to what I hope to achieve with the D800 and not as a comparision to the Hasselblad. I don't call this a test, as I'm not trying to evaluate lenses in a controlled scientific manner but, under more real world conditions using the same workflow that I use near daily. After all, that's the way we work.
I think I've seen the chart slices you have posted before, which gave rise to my including the Zeiss (and my respect for Zeiss) in the comparisons. But,at the moment, I am not seeing this profound difference between my copy of the 17-35 and the Zeiss 21. But, then again I'm just beginning the comparison of these three lenses and, hey, maybe I have a great 17-35 and the Zeiss is a poor copy.
We'll see as I move along with this during the week.