Sorry, but you are incorrect.
He was convicted of assault on LE, but the record was allegedly expunged once he completed a diversion program. That's not the same thing as having charges dropped, nor is it the same thing as being declared not guilty.
That's not what I read. Zimmerman was arrested and charged with assault on an officer. The charge was later reduced to a misdemeanor and dismissed, after Zimmerman underwent a diversion program which apparently included anger management. So, there was no conviction.
But, the point is, he is the only one of the two who has been arrested for violence, who had multiple other allegations of violence made against him resulting in a mutual stay away order and he is the only one of the two who has reported, aggressive behavior as complaints to both the HOA and to LE were apparently made by his neighbors.
Trayvon is reported as a gentle person. His brother and parents seem like gentle, soft-spoken people. Nothing has surfaced that actually evidences any aggressiveness on the part of Trayvon, as it has on the part of Zimmerman.
It's not rocket science. Zimmerman has an aggressive or violent background. He has a hero complex or control issues, evidenced by his years of repeatedly calling LE for various things and his stated desires to become an officer, that never were satisfied. Zimmerman is the one who followed an unarmed teenager who was walking, alone, even after the dispatcher stated he did not need to do that. Zimmerman is the one who was "fed up" according to his friend and who followed a person who he had not seen doing anything criminal, after stating, "they always get away".
Even without Trayvon's girlfriend stating he was scared that a strange man was following him and was trying to lose the strange man who later reappeared and confronted him, even without the 911 calls that reveal a youthful voice shouting in a panicked quest for help, it is clear who the aggressor was more likely to be. IMO.