Whisk the sauce: In a small bowl, combine soy sauce, honey, rice vinegar, sesame oil, red pepper flakes, chicken broth, and cornstarch.
Stir until smooth and set aside.
Prep the chicken and veggies: Pat the chicken dry and slice thinly. Cut zucchini into half-moons so they cook quickly but keep some bite. Slice the onion and bell pepper.
Mince garlic and ginger.
Preheat the pan: Heat a large skillet or wok over medium-high until hot. Add 1 tablespoon of oil and swirl to coat.
Stir-fry the chicken: Add chicken in an even layer. Season lightly with salt and pepper.
Cook 3–4 minutes, stirring occasionally, until just cooked through and lightly browned. Transfer to a plate.
Cook the veggies: Add remaining 1 tablespoon oil to the pan. Toss in onion and bell pepper.
Stir-fry 2 minutes. Add zucchini and a pinch of salt. Cook 2–3 minutes more, until just crisp-tender.
Bloom aromatics: Push veggies to the sides.
Add garlic and ginger to the center. Cook 30 seconds until fragrant, then toss everything together.
Sauce and combine: Return chicken and any juices to the pan. Give the sauce a quick stir and pour it in.
Stir continuously for 1–2 minutes until the sauce thickens and coats the stir fry.
Finish: Stir in green onions. Taste and adjust with a splash more soy sauce for salt, honey for sweetness, or vinegar for brightness.
Serve: Sprinkle with sesame seeds, add a squeeze of lime if you like, and serve hot over rice or your favorite base.