I've listened to the Z3 for extended periods, on multiple occasions.
I found very little wrong with them.
What really struck me. was a very natural sounding attack and decay. But I could not find any other major weaknesses. Detail was also about as good as I have heard.
Soundstage is also near the top of what I have heard. Image specificity, and layering, is world class. I got the impression, I could walk into the soundstage and grab the violist's bow from their hands.