A clarifying question that I was confused by when looking at the zoo on Google Maps: can you just walk into the zoo from the train station and vice versa? How did the two end up right next to each other?
No its not possible to walk from the train station directly into the zoo but as soon as you leave the station through the right exit you are standing in front of the entrance of the zoo.
That they are lying next to each-other has - I guess - some historical back-ground.