Please excuse me, but there was no 911 call.
Zimmerman called the non-emergency number and spoke with a non-emergency dispatcher. The City of Sanford issued a statement to this effect in March. The charging affidavit for Second-Degree Murder makes this clear, differentiating between Zimmerman's call to a dispatcher and the other "911 calls."
Zimmerman was advised by a non-emergency, non-911, police dispatcher.
But this is the immortal meme, doncha know. Or, maybe, the undead meme, because it eats the brains of the living.
So don't confuse us with facts.