Slice the chicken breasts into thin strips. Put them in a bowl and mix with the cornstarch, a little salt, and black pepper.
Wash the zucchinis and slice them into thin rounds. Mince the garlic and ginger.
Heat the olive oil in a large pan over medium-high heat.
Add the chicken strips to the pan. Cook for 5–6 minutes while stirring until the chicken is fully cooked and lightly golden.
Add the minced garlic and ginger. Stir for about 30 seconds until fragrant.
Add the sliced zucchinis to the pan. Stir fry for 3–4 minutes until slightly tender but still fresh.
Pour in the soy sauce, oyster sauce, and sesame oil. Stir everything well so the sauce coats the chicken and zucchini evenly.
Taste and add more salt or black pepper if needed.
Cook for another 1–2 minutes until everything is hot and well mixed.