I think it's Xebo, because it's the only big male in this exhibit. But the photo was taken at 2009 and I can't confirm you if Xebo was there or at the other exhibit at these time. Apes are not my favourites and I can't reconize them. Maybe other member can identify it.
If you want, in my next visit I'll try to take a picture of Xebo and i'll upload it here. Today I was at the zoo, but I only took photos of the young gorillas.