Prep the chicken: Thinly slice the chicken breast. Toss with 1 tablespoon soy sauce and 1 tablespoon cornstarch.
Set aside while you prep the vegetables. This quick marinade boosts flavor and keeps the chicken tender.
Make the sauce: In a small bowl, whisk soy sauce, rice vinegar, oyster sauce, honey, sesame oil, red pepper flakes, broth, and 1 teaspoon cornstarch until smooth. Adjust sweetness and heat to taste.
Heat the pan: Place a large nonstick skillet or wok over medium-high heat.
Add half the oil and let it get hot, just until shimmering.
Cook the chicken: Add the chicken in a single layer. Sear 2–3 minutes per side until lightly browned and just cooked through. Remove to a plate.
Stir-fry the vegetables: Add the remaining oil to the pan.
Toss in broccoli, carrots, and snap peas first. Stir-fry 2 minutes, then add bell pepper and zucchini. Cook another 2–3 minutes until crisp-tender.
Add aromatics: Push the veggies to the sides.
Add garlic and ginger to the center. Stir 30 seconds until fragrant, then toss everything together.
Combine and sauce: Return the chicken and any juices to the pan. Pour in the sauce.
Stir constantly for 1–2 minutes until the sauce lightly thickens and coats the chicken and vegetables.
Finish and serve: Sprinkle with green onions and sesame seeds. Taste and adjust with a splash of soy sauce or vinegar as needed. Serve over cauliflower rice or a small portion of brown rice for a low-calorie meal.