Soak corn in water to cover 1 hour. Peel back corn husks, leaving husks attached. Remove silks.
Spread Cilantro Butter evenly over corn, tomato, and zucchini; sprinkle with salt and pepper. Pull husks over corn, and twist ends tightly. Place tomato and zucchini in a grill basket.
Grill vegetables, covered with grill lid, over medium-high heat (350° to 400°) 10 to 15 minutes or until zucchini and tomato are tender, turning corn often. Grill corn 5 to 10 more minutes or until tender. (Husk edges will blacken.) Remove husks. Serve vegetables immediately. Garnish, if desired.