Zimmerman initiated contact, in an aggressive manner. The teen likely, and had reason to, thought his life was in danger. He had every reason to fight under the assumption his life was in danger.
I would to, under the known circumstances, and so would you as it would be very stupid to not do.
You do not know how Zimmerman acted toward Martin or what he said to him after he got out of his car.
You claim otherwise because you are a liar.