In a medium bowl combine 2 tablespoons light soy sauce, 1 tablespoon rice vinegar, 1 tablespoon sesame oil, 2 tablespoons corn starch for marinade. Add 1 pound boneless and skinless chicken breast and mix to coat; allow to marinate for 20-30 minutes or overnight.
Combine 1/2 cup water, 1/4 cup light soy sauce, 2 tablespoons oyster sauce, 1 tablespoon rice vinegar, 2 teaspoons brown sugar, and 1 tablespoon cornstarch for the sauce in another small bowl. Set it aside.
Heat 2 tablespoons vegetable oil in a large skillet over high heat. Once the skillet is smoking, add the chicken in a single layer (don't overcrowd the skillet to get a good sear). Cook until browned, flipping and mixing as needed. Once cooked, remove from the skillet and set aside.
Add 2 cups mushrooms and 1 large zucchini to the skillet and cook until vegetables are crisp tender ( about 2-3 minutes), mixing frequently.
Reduce the heat to medium low and add the chicken back to the skillet. Add 3 minced garlic cloves and 1 teaspoon minced ginger and cook for 1 minute, stirring frequently.
Finally, pour the sauce into the skillet, mix everything to coat. Stir fry until the sauce thickens.
Serve immediately. Enjoy!