I’d just ask her if her son is in the courtroom? She could point to GZ and I would say, “I have no further questions.”
IIRC one of Zimmerman’s best and life long friends is black. I believe I heard him interviewed on the radio last year. I would simply ask him if he knows GZ and what his relationship with him was. After he said “we are lifelong friends” I would say, OK, I have no further questions.
And he could also ask “Has your son ever volunteered his time to tutor black kids?”. Case closed.