Marinate chicken by combining soy sauce, garlic powder, ground black pepper and sugar. Mix well and set aside. Note: you can do this step before cutting your vegetables so the flavoring will seep into the chicken meat.
In a cooking pan/ wok, using high heat, cook garlic and onion.
Add marinated chicken strips and lower heat to medium. Cook until golden brown, remove from the wok/ pan and set aside.
In the same wok, heat oil and put the mushrooms, stir until somewhat soft.
Add the zucchini and mix thoroughly. Put the oyster sauce and add the green bell pepper. Cook for a minute. Season with soy sauce, salt and pepper.
Put in the spinach, stir until slightly cooked. Turn off the heat.
Combine the marinated chicken into the vegetables. Stir well until fully incorporated.
Transfer to a serving bowl. Serve and enjoy!