I'm not crazy about Zeller as a center in the NBA. He has a nice hook shot, I just don't see him as anything but spot minutes, imo. I also don't think he drops past about pick 20'ish.
I think there's a reasonable chance Barnes drops to 4 - 6. He should go 3, but it's a long season ahead.
If Zeller continues to improve like he has been and adds some more bulk I think he has a real shot at being a rotation player in the NBA. Very mobile and pretty athletic for a man his size. Agree that he will probably be a 1st rounder.