It's a Samango Monkey the zoo has a breeding and rescue program for them, Where in the Zoo did you see them? I believe they were all moved to Mokpane Biodiversity centre which is closer to their natural range
Here is the correct subspecies, I found it on one of the zoos old documents:
Mozambique Samango Monkey (Sykes' Monkey) Cercopithecus albogularis erythrarchus
