It doesn’t matter imo. Prosecutors are trained in the law, and qualified to make the call. Police aren’t. Investigators often want cases pursued that DAs don’t.
I have had many cases not prosecuted during my career, usually because the evidence was not so overwhelmingly strong that the government could plea it out rather than have to go to trial.
They were solid cases, but the government felt they weren't "slam dunks", so they got no-papered (not charged).
Alternatively, I have had cases where the law was technically broken, but I felt it did not rise to the level of criminal prosecution. In some such cases, I was required by law to make an initial arrest, but when I presented the case to the prosecutor I would actually request that it be no-papered (not charged). The prosecutor would generally honor such a request.
I bring this distinction up because the mere fact that a detective presented an affidavit or charging document to the prosecutor does not necessarily mean that he "wanted Zimmerman charged". He may be required to present his facts to the prosecutor in such a fashion (and likely is required to do so in such a serious matter as a death investigation).
I therefore wonder if ABC News simply spun a report that the investigator delivered his documents to the prosecutor for review into "he sought charges" and "didn't believe the story".