Absent a judge's order, it takes two parties to agree to settle. Were I George Zimmerman, I wouldn't be in a settling mood.
I take your point, but the willingness to settle depends on one's assessment of one's likelihood of winning. So it's conceivable he might decide it makes more sense to settle, although that decision probably wouldn't come at least until the discovery phase is over, and possibly not until all the trial testimony is over.