Crowd Pleasing Grilled Zucchini Caprese Sandwich

1 zucchini, trimmed and cut lengthwise into 6 slicesOlive oil1 T. minced garlicKosher salt, black pepperBalsamic vinegar4 ciabatta rolls, split and toasted8 large fresh basil leaves1 large tomato, thinly sliced6 ozs. Fresh mozzarella cheese, thinly sliced1. Heat large grill pan…