Grilled Zucchini Caprese Sandwiches

INGREDIENTS

• 1 medium zucchini, trimmed and cut lengthwise into 6 slices
• 4 teaspoons extra-virgin olive oil, divided
• 1 garlic clove, minced
• 1 1/2 teaspoons balsamic vinegar
• 1/8 teaspoon kosher salt
• 1/8 teaspoon black pepper
• 4 (2-ounce) ciabatta rolls, split and toasted
• 8 large fresh basil leaves
• 1 medium tomato, thinly sliced
• 6 ounces fresh mozzarella cheese, thinly sliced