Season chicken with salt and pepper, then toss in a bowl with corn starch until evenly coated.
Heat avocado oil in a large skillet over medium-high heat, cook chicken 2-3 minutes per side or golden brown and cooked through. Remove chicken from skillet and set aside.
Add broccoli, bell pepper, and zucchini to skillet – sauté for 5-6 minutes or until tender, but still crisp.
While veggies cook, whisk together all sauce ingredients in a small bowl.
Add cooked chicken back into skillet along with the sauce, reduce heat to low and cook for a few minutes or until sauce has thickened.