Create a false dichotomy and then apply Occam’s razor? Shame on you.
Here’s a scenario: Zimmerman confronts Martin, who tells him to fuck off. Zimmerman escalates, gets closer and tries some sort of bullshit MMA move. They end up rolling on the ground, which accounts for the various bumps and scrapes he received. They momentarily separate at which point Zimmerman draws his weapon and discharges it.
I know this violates your need for Martin to be the aggressor, but it too is plausible, and considering that Zimmerman was taking MMA training and already torqued up and apparently not listening to reasoning prior to exiting his vehicle, more likely.
