In a bowl, season the chicken with ½ tsp each salt, pepper and garlic powder. Toss with 1 tbsp cornstarch until evenly coated. Set aside.
In another bowl, whisk together all the sauce ingredients until combined. Set aside.
Heat 1 tbsp vegetable oil and 1 tsp sesame oil in a large skillet over medium-high heat. Stir-fry the zucchini, bell pepper and onion until tender-crisp, about 3-4 minutes. Remove veggies and set aside.
Add the remaining 1 tbsp vegetable oil to the skillet. Cook the chicken in a single layer until browned, about 2-3 minutes per side. Add the garlic and ginger and cook until fragrant, about 30 seconds.
Pour in the sauce and bring to a boil. Simmer until thickened, stirring occasionally, about 1-2 minutes.
Return the veggies to the skillet and toss to coat in the sauce. Cook until heated through, about 1 minute more.
Serve hot over rice and garnish with sesame seeds and green onions if desired. Enjoy!
