Cook the noodles according to package directions.
In a small saucepan combine all the ingredients. Heat over medium until thickened.
In a large skillet fry onion for few minutes, adding water to prevent sticking. Add bell pepper, oyster mushrooms and cook for 5 minutes. Add zucchini and cook for additional 5 minutes. Add sauce and cook for 2 more minutes. Add noodles and combine everything together.