Translation:He is finishing his career in a zoo.
What would be the context of this question? i.e. a retirement party in a zoo ( as previously stated ) say someone had a specific job, say a cleaner and his last assignment was in a zoo, he worked in a place that became a zoo, someone had several different jobs, the last of which was in a zoo?
The English "He is finishing his career in a zoo" makes it sound as though he left some other job (perhaps working for a vet) and will work for the zoo until he retires.
However, I strongly suspect that the French sentence means "He is ending his career at the zoo." We rarely say "a zoo" for something like this, much as we say "I went to the doctor" not "I went to a doctor."