I've only had one experience with a Zeiss scope.
I was at a range in NC, near Camp Lejeune. Guy beside me was trying to sight-in his new Rem 700 300RUM. Had a brand new Zeiss 3.5-10x50 (or something close to that) on top. After a couple "groups" were not materializing he asked me if the scope looked OK to me. I had a look through it, everything had gone quite yellow, and the reticle was canted about 20 degrees out.