8 ounces orzo (about 1 1/3 cups)
6 1/2 tablespoons extra-virgin olive oil, divided
4 tablespoons red wine vinegar, divided
2 medium zucchini or summer squash (about 9 ounces total), cut lengthwise into 1/4-inch-thick slices
1 red or yellow bell pepper, quartered
3 tablespoons purchased pesto
2 tablespoons fresh lime juice
1 pound uncooked large shrimp, peeled, deveined
2 heirloom tomatoes (8 to 10 ounces total), cored, cut into 1/2-inch cubes (about 2 cups)
1/2 cup thinly sliced fresh basil leaves plus sprigs for garnish
1 8-ounce ball fresh mozzarella cheese, cut into 1/2-inch cubes