Three things:
First, if you're looking for a job, the Zimmerman trust fund is a little short, and no such thing needs to be done. The exact conditions of that night cannot be reproduced, and you have examplars from GZ videos at the scene that can be used and probably already have and the tenor of his voice has probably been linked to the cry for help as opposed to the deeper voice of TM as at the 7-Eleven or recorded on Martin family tapes and phones that they won't turn over.
Second, an authoritative witness already identified the voice as GZ's -- his father -- and that testimony is on the record. Another witness John has also identified it as coming from the guy on the bottom getting his head bashed in, and that testimony though not yet made in court is also on the record. And lying Sybrina won't dare take the witness stand to defend her on the record prefabrication because TM's father already said it was not TM.
Third, unless you wrote that article under oath, you are not on the record. Common sense is your best expert and it tells you who was calling for help -- the guy on the bottom getting his head bashed in, and that was George Zimmerman.
The voice crying for help is clearly that of Zimmerman. And, according to early reports, Trayvon's father originally stated it was not his son, but changed his story after the race pimps came to town.