Zero likes hugs. And cuddles, and tender contact. When it comes to being with someone, he most favors affection because he isn't interested in rough lovers. Someone who is at least capable of being gentle with him could be enough if he feels attracted towards them.
Basically, Zero isn't into the rough lover type. He can be emotionally, and oftens times physically sensitive. He's got a mature mind, but he likes when he's able to make friendships with people who respect him and are just there if he needs someone. He's a friendly, pretty civilized guy tbh.
Someone like Frost or Hit would probably be as far as he'd get into having an "intense" partner. But he appreciates if his partner is able to/ok with holding back during moments of intimacy, because Zero can become startled or overwhelmed if they get too rough with him.
He knows what he wants and hopes his partner will understand that and respect what he likes without taking advantage of his more sensitive side.
So tender love making with passion large enough to make both him and his partner feel good is liked on his part. He wants them to be happy, too, after all :)
Of course, he still has his own personal space bubble like most people, so he's definitely not a constant affection lover unless he's in the mood or needs it ^.^