Just to correct some information in the main review, Zest is now closed on Tuesdays at the time we visited (December 2012). They have a simpler day-time menu from 11am to 6pm and a full, evening menu after 6pm.
We were only in Leipzig for one day and partly made the trip so we could try Zest. We were only able to visit for the day-time menu, but it was great. Lots of options that look relatively good on the menu but are fantastic and subtle when we got them. My partner and I are both vegan and really the menu is almost 100% vegan. (The website indicates that the only non-vegan items are well-marked cheeses, but I didn't see any non-vegan cheeses . . .)
I had a focaccia with seitan and a side of vegan potato salad (German-style, and a very impressive version of the tradtional), while my partner had a great burger (one of the best vegan burgers I've tried anywhere) with light, delicious curly fries. For dessert I had a soya fudge chocolate brownie (decadent and delicious) and my partner had the brazil-nut carrot cake with marzipan icing. It was a a fantastic, relaxed experience and a highlight of our time in Leipzig. I would definitely go back just to eat there and would love to try there evening menu.
It's about 4km from the city centre in a very interesting area of Leipzig with easy public transit connections (tram).
We spend a lot of time in Berlin and there are some great vegan food experiences there (Mano Verde, Lucky Leek, Vaust, etc.), but Zest is right up there I think in terms of culinary excellence (though a bit more laid back in style and atmosphere). Definitely worth a visit if you happen to be in Leipzig.Pros: great food, diverse, creative menu, relaxed neighbourhood atmosphere
Cons: distance from city centre