Good one! ... when I read the title I thought you bought a ZEISS lens that did not live up to its name.
At least my endodontist uses top-shelf equipment
As far as Zeiss, I did just return the Sony/Zeiss FE 55 mm f/1.8 when I returned the A7R. The lens was sharp as heck, but I did have one issue with it. It's minimum focus distance was a pretty far 50 cm with magnification of only 0.14x, which was a hair too little for close-ups or near-macro's ("ring shot").
I guess I'm just spoiled by my EF-M 22 mm, which can do 1:2(!) macro at 15 cm and even by my 35 L which can do 30 cm at 0.18x, which was a big difference in practice.