Then again...
Maybe you were there and saw the whole thing. We'll just go by what you present as facts. The heck with anything that doesn't fit your narrative.
He told the operator that he wasn’t going to let the kid get away, that implies that he’s going to confront. Even if the kid was running, he can’t out run a car. Zimmerman could still observe and report from his car, if that’s all he was trying to do.
Zimmerman told the operator that he was going to not let the kid get away and got out of his car. The only legitimate reason for leaving his vehicle is because he’s going to do more than just observe, he was going to try and apprehend the person.