Isn't this one of the ungulate enclosures on the perimeter of the zoo, for zebras, oryx, wildebeest..? There may be an oryx at the top left of the picture - although my eyesight is not good enough to be sure (it may well be a plant or something...).
The animal you spotted is more likely an Oryx than a Wildebeest; I remember the former but not the latter, although it was of course 9 years ago. Until one of the Dutch members comes to my rescue with a confirmation, I will rename this an Oryx exhibit.