No word on apertures or bodies used for the test, but judging by the different magnification, the Nikon and Zeiss were probably tested on a higher MP body than the Sony and the Sigma. Although having said that, both the Nikon and Zeiss are longer than 50mm.
I'm guessing the Nikon and Zeiss were on a D800, and the Sony was on a 24mp FF body. The Sigma looks to be tested on the same resolution too, but I'd have thought Sigma would make a Sony mount last, so possibly Canon mount on an A7?
Anyway, to me the Sigma appears slightly better than the Zeiss - but this doesn't reveal much - clearly different post processing, lower MP to hide problems, and no word on what aperture setting was used.