Our dog enjoyed the visit very much. She can visit most of the zoo with her leash on. But you have to give up certain areas as they are dog-forbidden and we totally get it (e.g., bird paradise, which will be dog paradise and bird hell if dogs are allowed to visit). 
Definitely not recommend to get there on foot, as it was really tiring. We went to O-muro Mountain after that, the view was terrific.