Somebody told Zimmerman what he should've done, and Zimmerman chose not to do that. Probably now to his eternal regret.
That's possibly true. It's also possibly false. From the evidence so far publicly available, I don't see how we can be reasonably certain whether Zimmerman did or did not continue following Martin after being advised not to.
It is unfortunate that the dispatcher was not more direct in their statement to Zimmerman, : "We don't need you to do that" (meaning follow anybody). Still, it was the proper advice.
I agree. The dispatcher was absolutely correct to advise Zimmerman not to follow anybody, and it's unfortunate that he did not deliver an explicit instruction instead. Still, we don't know from the tape alone whether Zimmerman complied with the dispatcher's warning or ignored it, or who approached whom and initiated the conflict. If there is some credible evidence that would settle this matter, I haven't seen it yet.