While I don't have enough knowledge to agree or disagree with either one of you, now that I know it is some kind of Capuchin at least, I looked at the Zootierliste and the only Capuchin species they have at present is Weeping Capuchin, or Weeper Capuchin as they call it.
Although I cannot be totally sure (at least until a German zoo enthusiast comes to my rescue) chances are overwhelming that this is what Nicholas suggested.
