I did a bunch of more controlled comparisons with the two. Here are my conclusions.
a. The CY version is slightly wider than the ZE.
b. The ZE is slightly sharper than the CY at f2.8. CY slightly sharper than the ZE at f5.6. Beyond that they are equal.
c. The CY meters about 1/3 stop brighter at every aperture. The ZE appears more accurate.
d. CY is also warmer by about 300K (Camera on AWB).
e. CA is about the same on both across the apertures. If I split hairs, I would give the nod to ZE esp. wide open.
f. Weight. The ZE is so much heavier than the CY. Whats with that?
I like the other intangibles i.e. auto aperture, EXIF etc. for the ZE.