I took the children here on our first day in Zurich - buying a joint tram / zoo entry ticket from our local tram station (Bellevue) - and then travelling there easily up the hill via two trams (5 and 6)).
We arrived early as the zoo opened and on a weekday in April found the zoo very quiet. There's plenty to see and you could easily spend half a day to three-quarters of a day there (as we did).
The zoo is laid out in regional zones, and the range of animals is excellent - including: hippopotamuses, rhinos, tigers, lions, camels, penguins, a very good gibbon house (lots of fun watching them), orangutans (my favourites) and gorillas - including 6 month old babies at the time of our visit, a good aquarium and reptile building and the the well-known Masoala Rainforest - a rainforest houses in a large indoor building which was very well created.
We had a good lunch at the restaurant attached to the Masoala Rainforest area (with a Madagascan theme) - though it was expensive of course.
There's a huge amount of work going on at the moment to expand the zoo - including a huge elephant enclosure and African savannah section. These will make the zoo even more unmissable.
Overall, a great day out with family during a short stay in Zurich.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.