You have no idea who started the fight and unless an eyewitness comes forward willing to testify that Zimmerman physically attacked Martin first there have been no laws broken if one witness has stated that Zimmerman was on his back on the ground getting beat up . If it was his voice screaming for help that corroborates the witness’ statement.
“You have no idea who started the fight..”
Neither do you. What we do know is that Zimmerman was the initial aggressor as he was pursuing Martin. Why was he chasing Martin? Citizen’s arrest? Detain him for the police? Search him? Check his ID? Chase him out of the neighborhood? Zimmerman did not have the authority to do any of those things.