I can actually see Zhao Zi having A Thing for Actually Scary Intense Jack during sex.

Remember, he was not afraid of Jack when Jack hauled him in for interrogation, even after Jack physically threatened him. And Zhao Zi is the one who pushes Jack up against the wall during their third kiss after Zhao Zi accepts Jack as a member of his family.

I'd like to think that Zhao Zi might get turned on by Jack being a little dangerous. I think it's totally doable and believable.