Wash the chicken breasts and slice them into thin pieces. Put the chicken into a bowl and add cornstarch, a little salt, and black pepper. Mix well.
Wash the zucchinis and slice them into thin rounds. Mince the garlic and ginger.
Heat olive oil in a large pan over medium-high heat.
Add the chicken slices to the pan. Cook for 4–5 minutes until the chicken becomes golden and fully cooked. Stir often.
Add the minced garlic and ginger. Stir and cook for about 30 seconds until fragrant.
Add the sliced zucchinis to the pan. Cook for 3–4 minutes while stirring gently.
Pour in the soy sauce, oyster sauce, and sesame oil. Mix everything well so the sauce coats the chicken and zucchini.
Taste the stir fry and add more salt or black pepper if needed.
Cook for another 1–2 minutes until everything is hot and well combined.
Turn off the heat and serve the Chicken Zucchini Stir Fry warm.