In shallow dish, marinate flank steak in hoisin sauce, in the refrigerator, for 4-6 hours or overnight.
Preheat grill. Meanwhile, toss peppers and zucchini with oil and peppeer.
Place steak and vegetables on grill. Cook steak for 8- 10 minutes, turning once or until desired doneness. Cook vegetables until tender-crisp, turning once.
Remove steak from grill and allow to rest for 5 minutes. Slice steak across the grain into 1/4 inch (1 cm) slices. Serve with grilled vegetables.