1In small bowl, mix Garlic-Lemon Mayonnaise ingredients; set aside.
2Heat gas or charcoal grill. Brush zucchini and mushroom caps with oil; sprinkle both sides with salt and pepper. Place vegetables on grill over medium-high heat. Cover grill; cook 6 minutes, turning once, until just tender. Slice mushroom caps; cool.
3Spread Garlic-Lemon Mayonnaise on cut sides of bread. On bottom halves of bread, layer zucchini, mushrooms, chicken, tomato, cheese and basil. Cover with top halves of bread.