Zuzu's is only a few blocks from my office, and I've been there twice for lunch with some work friends. It has a casual atmosphere, with plain lunchroom tables and chairs and a high, open ceiling. You order first at the counter and take a number before sitting down to enjoy your chips and salsa.
As a connoisseur of Mexican cuisine, I found the food so-so. The enchilada sauce doesn't exactly taste like any other enchilada sauce I've had. As a matter of fact it tends to have a suspicious Italian flavor. The black beans are good, although I tend to prefer the more traditional refried beans, but the rice is not very spectacular. I've made better mexican-style rice at home. I also wished for a little sour cream or guacamole (which you can get as a side, but doesn't come with the meal).
Service, again, is ok. The prices are maybe a bit high for the quality of food, but not outrageous. Do get there early, because it fills up at lunchtime!
Overall, it's a pleasant place to stop for lunch, but not outstanding if you're looking for good Mexican food.