Apparently, you don't believe it. Why?
Because Zimmerman is the interested party, d’uh! Electric chair or walk free, do I have to spell it out? Apparently so. Not a word he says is believable.
Let’s imagine just for argument’s sake, that Zimmerman had a previous encounter with Martin who must have visited the complex before, and that Zimmerman was set on a revenge and murdered the kid in cold blood.
What do you think his statements would have been afterwards? He wouldn’t say that he shot the kid in self-defense? Ignore the above - WHEN would he not say that he did shoot the kid in self defense?
All we know in this case for certain are the 999 recordings and the police report. EVERYTHING ELSE is pure Rashomon, witnesses, killer’s statements (especially!), it’s all speculation and conjecture.