Yes you can help him to get over his fear of hands. After all that's what it is. He wants to be with you and considers you his mate or at least flock mate (your a friend). Somewhere ,sometime he had a bad experience with hands. Or he might percieve them as "rivals" but that's usually more conure size birds.(Same is true with cell phone,mouse,toothbrush,etc). With a zon it's because of being manhandled or "hands always mean i'm doing/going somewhere i don't want. Either way the cure is the same. Trustworthy ,confident, and most of all a view of the world though your birds eyes. When "stepping up" don't be demanding, but offer with out fear of bites, if he does great ,but if he doesn't don't ask again and act as though he's missing out. Of course pick your battles and ask when your sure he's receptive, when he does step up ,quickly put him back down. Don't let "stepping up" mean "i'm going to pet you" or "i'm going to move you". Stepping up only means stepping up . If he's on the floor and wanting up, quickly put him where he wants to go. Don't try to turn it into a petting session. When you start petting him while outside the cage , remember to only give him short doses of attention. End each interaction with him wanting more of your attention instead of him biting you to say, "I've had enough". He wants to fit in ,but doesn't know if your hands are to be trusted. Work with it and before long you'll be making huge leaps and bounds. Zons just want to have fun and be loved. Good luck.