I can't post links yet, but if you search for Android Central blind camera shootout there was a recent one on October 15 that pitted the Z5 against the 6s, Note 5 and G4. The Z5 finished 3rd, but ahead of the well-regarded G4, so that indicates to me that the camera is decent, but perhaps not as good as dxomarks more technical measurements would indicate.
Two things from the shootout (and other recent reviews) that I'm unsure about:
1) 8M overscan mode (the default) vs 23M hi-res mode. I'm still unclear when to use each, and what impact it has on quality in different situations. Someday I hope to find a well-written guide, or I'll have to experiment when I get my own Z5 (order today).
2) I think Sony released an updated software camera app in October. Not sure if this affects picture quality, or was more geared towards ease-of-use and speed of app opening up, and whether the shootout included this new app or not.