We visited the Zoo on a Wednesday, it wasn't crowded at all. The Zoo is stroller and wheelchair friendly with ramps, although it is an uphill walk so it got quite difficult in the stifling heat. UV umbrellas and shades are a must during the summer! We would have stayed for longer if it wasn't for the heat, but nonetheless great fun for children and adults, highly recommended!
NT$60 entrance fee is just insanely cheap for a zoo - London Zoo cost around 20 times that!
You can hire strollers (NT$50 hire plus NT$500 deposit) and wheelchairs (NT$1000 deposit) just inside the entrance.