Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat. Add bite-sized pieces of boneless skinless chicken breasts and sauté for 5-6 minutes until golden brown.

In the same skillet, add another tablespoon of vegetable oil, minced garlic, and ginger. Sauté for about 30 seconds until fragrant.

Add sliced mushrooms and zucchini to the skillet. Stir-fry for 4-5 minutes until tender yet crisp.

Return the chicken to the skillet and pour in soy sauce and sesame oil. Mix thoroughly and sauté for another 1-2 minutes.

Prepare a cornstarch slurry with water and add it to the skillet, stirring constantly until the sauce thickens.

Fold in chopped green onions and cook for another minute, adjusting seasoning with salt and pepper as needed.

Serve the stir fry over a bed of steamed rice or noodles, garnishing with green onions or sesame seeds if desired.