The transcripts of the phone calls make it improbable that Zimmerman initiated the violence.
Zimmerman tells the dispatcher that Martin is running and exits his truck to follow.
Martin tells his girlfriend that he`s lost Zimmerman (which is corroborated by Zimmerman telling the dispatcher he`s lost sight of Martin).
Zimmerman never caught Martin. How is he supposed to have initiated violence
If Zimmerman left the safety of his truck to go after a guy leaving his area, whether walking or running, is proof that Zimmerman was not being threatened.
Zimmerman has no probable cause to go after Martin.
If Zimmerman never caught Martin, how could there have been a fight.