A zoo is too good for them. The ACLU would have them released on human rights and PETA charges.
Here is a stupid idea.
You take every terrorist who fought against America, line them up on a wall and put a bullet in each ones head.
Basically, you fulfill the Geneva Convention obligation that someone who fights against a nation who is not a soldier of that nation has no rights.
The ones who didn’t fight, but got caught up in all the action get sent back to their host country. Airfare would cost about 1/4 million and bullets at todays prices would cost about the same.