Old bird trainers trick. Wrap a towel around each forearm. Wrap that up with ace bandages to keep it in place. Put a loose fitting shirt on over the towels. Now the bird doesn't know they are there and won't be distracted by, or afraid of them.
With a zon, you tuck your thumb into a fist. (They generally go for the thumb.)
Keep a bent fist so there is nothing to latch onto, therefore biting the hand is ineffective. They will attempt to bite your toweled forearm.
Step them up on your forearm. Basic step up, no biting exercises.
When they accept that you move on to basic touch exercises, which I do with two wooden BBQ skewers. Once he accepts touching with the stick, you gradually move your fingers down, until you are touching him with the fingers.
And it is a fact: wild birds don't generally bite as hard as captive bred birds. The reason for that is that captive bred birds have no fear of humans, where the wild bird is still going to be hesitant and afraid. Winning his trust and getting him to allow it the first few times is going to be the battle. Once you get past that point you're golden...
In the wild, fights that cause injury can mean death. They will warn you away rather than attempting to injure. His first instinct is flight, not fight.
