In a small bowl, whisk together the barbecue sauce, maple syrup, soy sauce, and rice vinegar. Set aside.
Heat a large skillet or wok over high heat. Add 1 tablespoon oil. Sear beef in a single layer for 2 to 3 minutes undisturbed. Stir and cook 2 more minutes. Season lightly. Add ginger, garlic, and orange zest; stir-fry 1 minute.
Pour 3 to 5 tablespoons sauce over beef. Toss and cook 1 minute until coated. Transfer to a plate and keep warm.
Add 1 tablespoon oil. Cook mushrooms 5 minutes until golden. Transfer to plate.
Add remaining oil. Stir-fry onion, zucchini, and bell pepper 7 to 8 minutes until tender-crisp.
Return beef and mushrooms to pan. Add more sauce if desired. Toss briefly until heated through.
Sprinkle with sesame seeds and serve over steamed rice.
