I wonder if the child abuse charge is smoke and mirrors to draw attention from the added 3rd degree murder and manslaughter. (Argue this while we slip in that.)
No, the child abuse charge is necessary to allege Felony Murder. Felony Murder says that anyone you kill in while in the commission of a crime, even if the killing was unintentional, is murder. For that to apply, Zimmerman had to be committing a felony separate from the shooting itself for the shooting to be murder. So they are alleging child abuse as the felony to get felony murder charges included. But the prosecution is arguing that the shooting is what constitutes child abuse, which makes the shooting a felony, which make it felony murder. Kind of a circular logic there.