The ZE is sharper at the minimum focus distance and F2 - not much surprise there since it's a macro lens. Contax has a smoother, more diffused bokeh. I like the Contax better, but the adapters are tiresome. The difference in bokeh is subtle, but it's there. The ZE might have a smidge more CA at F2. I like the ZE for the auto aperture and smooth mounting / dismounting. The Contax might have the edge in its signature - but post processing will totally negate that edge. It's a very tough race to call. If Conurus offered a RTS to EOS conversion with auto-aperture, I'd pick the Contax for sure.