You are incorrect. Zimmerman started to chase Martin after Martin started to run. The dispatcher at the SFD asked if he was pursuing, he said yes, dispatcher said you don't need to do that, Zimmerman said okay. Stopped and stated to dispatcher that he didn't know where Martin was. Listen to entire Zimmerman call to SFD. You can find a link in post #33 on this thread.
I did listen to the entire phone call, several times. Yes, while on the phone Zimmerman stopped chasing the kid. But he knew what direction the kid was heading. When the police suggested meeting up with Zimmerman at the mailboxes, he hesitated and then replied that they should call him so he could give them his exact location. That suggests to me that Zimmerman, after getting off the phone, ran after the kid and caught up with him in someone’s backyard.