If Zimmerman had seen a young white man walking in a gated community with a hoodie that young white man would be alive today because GZ would not have been driven by the social stereotyping that persuaded him that this non-white mam was in fact a criminal, before he approached this lad he had made certain assumptions and had linked this boy to robberies, because he thought the guy was black. His attitude/demeanour when he approached and confronted TM was not going to be friendly one, possibly hostile, possibly aggressive.
In this situation, TM goes into fight or flight mode and has to decide what to do, at a guess he got a bit nervous, emotions are racing, he was probably aware or became aware that this older heavier man approaching him is a bit fired-up and probably has a weapon as he would know anecdotally of estate security guards, especially if he was casing the estate.
GZ, despite police advice to the contrary which he ignored, initiated a confrontation with a teenager doing nothing wrong and in the altercation that followed he shot dead a young 17-year-old man.
How long before we get the book, the film, the TV series, the exclusive story from Zimmerman, you have a strange way of creating some of your heroes, Jessica Lynch and Amanda Knox spring to mind.