I know Zach (not as a friend but as an acquaintance from Michigan State), and we have a lot of mutual friends, so I'm a fan and not trying to bash him or anything, but his game is unpredictable because his problems are all mental. He has the size and talent to average upwards of 20/10 every single night if he wants to, but there's no telling what kind of attitude he'll approach the game with.
I saw him in that Blazers practice on NBA TV last month and he seemed really unresponsive to coach McMillan's instructions and half-assed the drills, but judging by his early play (26.0 ppg, 10.3 rpg), you'd think he's got his act together. It's just a very unpredictable situation with him.