Marinate the chicken with soy sauce, apple cider vinegar, and sugar for 10 minutes.

Prepare the sauce by whisking together remaining soy sauce, vinegar, sugar, ginger, garlic, water, cornstarch, and red pepper flakes.

Heat 1 tablespoon of olive oil in a skillet and cook marinated chicken until golden brown, about 3-4 minutes.

In the same skillet, add another tablespoon of olive oil and sauté the onions for 4-5 minutes.

Pour in the prepared sauce and let it simmer for 30 seconds until slightly thickened.

Add the zucchini and cook for about 3 minutes until just tender before returning the chicken to the skillet.

Serve hot, garnished with sesame seeds and green onions.