Creating the Chicken Zucchini Stir Fry is straightforward when you follow these simple steps:

1. Prep the Ingredients: Gather and slice all the ingredients as indicated in the ingredient list.
2. Heat the Oil: In a large skillet or wok, heat the vegetable oil over medium-high heat.
3. Cook Chicken: Add the chicken strips to the skillet, cooking until golden brown and cooked through, about 5-7 minutes. Season with salt and pepper while cooking.
4. Add Garlic and Onion: Stir in the minced garlic and sliced onion, cooking for an additional 2-3 minutes until the onion becomes translucent.
5. Incorporate Vegetables: Add the sliced zucchinis and bell peppers. Stir-fry for about 4-5 minutes, ensuring the vegetables remain crisp.
6. Combine Sauces: Pour the soy sauce and optional oyster sauce over the mixture. Stir well to coat all ingredients.
7. Thicken (Optional): If desired, mix a teaspoon of cornstarch with a tablespoon of water to create a slurry. Pour this mixture into the stir fry and cook for an additional minute to thicken the sauce.
8. Garnish: Turn off the heat, and garnish with sesame seeds and chopped green onions, if using.
9. Serve Immediately: Serve hot over rice or noodles, enabling the rich flavors to shine.

Following these steps ensures a delightful chicken stir fry that brings aroma and flavor to your kitchen.