The first thing Everett does when he gets some alone time with his prisoner is beat and rape him. He gasses Zemo in his cell and--while the drugs kick in--explains exactly what he's going to do to him. Zemo still puts up a fight--he is ex-Special Forces, afterall--but Everett kicks his ass in his impaired state. He uses the fact that Zemo has nowhere to run to his advantage, and shocks/hits Zemo everything Zemo "raises his voice".

bonus:

--Everett getting annoyed when Zemo starts to go into shock, being annoyed that Zemo isn't giving him his full attention (it's a bit of a berserk button of Everett's) and Zemo dazedly telling Everett "I'm supposed to be dead by now"

--would love Everett to be satisfied physically (he's reduces Zemo to tears and blood) but also dissatisfied that he can't break someone who's already so broken