This restaurant serves vegetarian food since 1898! Greatest selection of very good vegetarian cusine in switzerland! Try the salad buffet with over 40 dishes and the indian buffet too. Whenever I go to zurich I stop at hiltl. They also serve great fresh pressed juices.
The restaurant is always fully booked, pre reservation is necessary if you want to go at a certain time. If you come and leave early you get some discount.