It's not really Zeller's fault. He was thrown into the starting role by necessity. He's really not meant to go up against guys like Drummond at all. He's much more suited to coming off the bench. That said, you're right. Drummond abused him tonight.
The interior defense as a whole was just awful. I lost track of the number of times the defense let a guy cut to the hoop, receive a bounce pass, then make a wide open layup/dunk. Games like this make me want Noel even more. He'd do wonders for this team and would be much more able to defend guys like Drummond. Drummond could still out muscle him, but I think Drummond will be able to out muscle most guys in the league.