I think he goes overboard on some of the relativistic language. Overall I find it good, though.
Some seven years ago I read an article of him translated into Serbian and published in newspapers of a Serbian diocese. It was the time of my blissed ignorance, when I was unaware about ecumenism/antiecumenism, existence of Old-Calendar schism in most Patriarchates and actions been taken by Constantinopolis for 80 years.
The article made me feeling physical pain.
Unlike Orthodox writers, whose writings flow like a powerful river, sound like a beautiful song, that article was quite different.
The conclusions, although seemed Orthodox, were based on arguments that were not related and proper for respective conclusion. Basically it's flawed way of thinking. The entire course of thought were not a flow, it was zig-zag line.
I was shocked and more Orthodox writers I read later, I felt better. So I basically don read him anymore. I forgot what was the article about - it was so destructive to me.
Yet another argument of his supporters is that we, his opponents, don't understand him, because we aren't educated enough. Fine.
Any carpenter can understand St. John of Damascus, St. Gregory the Theologian, St. Athanasios the Great and it doesn't take much education for it.
The same goes for most contemporary Orthodox theologians, but not for Metr. Zlizloulas. Though there is some similarity with Roman Catholics in the sense they too cannot take a grasp of their theology without much education, so they need and infallible Pope to tell them what to believe.
My final judgment is that his teaching is aimed at rephrasing Orthodox Faith to base it on false and flawed arguments, unlike the arguments used by the Holy Fathers to reach the same conclusions. Consequently, once we base our Faith on writings of Metr. Zlizloulas and forget the Holy Fathers, although there would be no difference in conclusions, we would be building on foundation of sand.
I won't read him anymore, it's destructive for my soul.