OK, so here goes. I tried a number of lenses, some of which I own and some not. Methodology was: from tripod, with timer, in RAW, processed in LR 3 (default settings), SOOC, fixed f:5.6., significant crop close to centre of image, all shots as closely spaced as possible to minimise light change. Out of a total of 9 lenses, spread over three sessions on three separate days, I will show "only" the Zeiss 24mm ZA, and a Leica 24 Elmar f:3.5 (same session). Please note that for some reason the EXIF is not always correct, the ZA shwong as "24mm" and not its full indentity. Also, being disappointed at the first quick ad dirty shots was so unexpected that I tried two copies of the ZA to eliminate chances of a "bad copy". They were essentially identical.
For reference, in total I did 3 types of shots, one close up, one at mid distance, one at infinity, all findings concurring. And I am usually very Neiss with Zeiss, as 11 out of the 12 alt lenses I own are from them, this being the first case of my not buying one of their designs. As a consequence, I ordered a Leica Elmar 24 (slower, MF, twice the money), so I wish the ZA had lived up to my expectations.
DISCLAIMER. I am not a tester. I stand to gain nothing from posting these shots. No link to any Website with advertising. No interest in self-aggrandizing self-promotion. I have no vested interest in this matter, as I have already tested the lenses to my satisfaction, so, if I am doing it, it is with the intent that sharing will let others think and (maybe) learn something of value to them. If you flame me because (a) I did not do the "right" shot, or (b), I did not do it "properly", or (c) I did not come to the "right" conclusion, all you will achieve is that I will no longer post a comparison like this on this forum, which takes some time. But you are entirely welcome to disagreeing in any way you feel appropriate, as I do not, sadly, have any copyright on "the truth", much as I wish I had...
Fist pic is Leica Elmar, second is ZA 24.