Ran this tonight, had a great time. My table decided to play up so I have very little pity for them.
The quick strikes ability from the black dragon zombie can be brutal. It killed the cavalier and scared the hell out of everyone else. Good thing zombies lose special attacks like breath weapon. It was also a good thing that it didn't have DR 5/slashing.
I almost tricked the table into releasing the glabrezu. So close I could taste it. But they persevered and it was awesome.
Overall a great scenario I thought.
Shane