In a mixing bowl, marinate the cubed chicken breast with 2 tablespoons of soy sauce. Allow it to marinate for at least 30 minutes in the refrigerator.

Heat a large skillet or wok over medium-high heat, and add a bit of olive oil.

Once the oil is hot, add the marinated chicken, and sauté until it's cooked through and no longer pink. This should take about 5-7 minutes. Remove the cooked chicken from the pan, and set it aside.

In the same pan, add a bit more olive oil if needed. Add the chopped garlic, minced ginger, and red onion. Sauté the mixture until the onions become translucent.

Add the green and yellow zucchini to the pan with the sautéed onions, garlic, and ginger. Continue to cook, stirring frequently, until the zucchinis are tender and slightly caramelized. This will take about 5-7 minutes.

Return the cooked chicken to the pan with the sautéed vegetables.

In a small bowl, mix the remaining ¼ cup of soy sauce with the cornstarch until smooth. Pour this mixture into the pan with the chicken and vegetables.

Stir everything together and cook for an additional 2-3 minutes or until the sauce thickens and coats the chicken and vegetables evenly.

Season with salt and pepper to taste. Add crushed red pepper at this stage for some spiciness, if desired.

Once everything is well combined and heated through, the Chicken and Zucchini Stir-Fry is ready to be served over rice or noodles!