This isn't even worthy of discussion. Maybe 5 strong men, but 12 is just too many. They would just pile on top of the gorilla.
Sure, some would get hurt real bad in the process, but there is no way on earth a gorrilla will be able to get out of a 12 man dog pile, then throw in the fact these are large strong men.
IIRC, these animals are 4 times as strong as humans and their bones 7 times as strong.
I think they say an average adult male could bench press somewhere in the 400 range. Doesn't sound like a lot, but considering they have never worked out, etc...
If they worked out, I'm sure their max BP would be somewhere in the thousand something.
12 men, in an enclosure? 99 times out of 99, the men win.