I visited the DOSBox site and noticed that version 0.71 was released about a week ago - and they fixed the bug on OS X that slowed ZZT down unbearably after a couple minutes of play.
dosbox is the way to go. but once i was playing a mirror image game on zzt using dosbox and the opening logo lagged like crazy. it took 10 minutes just to get your guy at the bottom for the game to start