In a large skillet, cook steak over medium-high heat, in 1 tablespoon oil until meat is no longer pink; drain.
Remove and keep warm.
In the same skillet, saute peppers in remaining oil for 2 minutes or until tender. Stir in the zucchini, onion and garlic; cook and stir 2 minutes longer.
Add the peas, mushrooms and water chestnuts.
Saute the vegetables for 2 minutes or until tender.
Return beef to the skillet.
Combine the cornstarch, broth and soy sauce until smooth; gradually stir into skillet. Bring to a boil; cook and stir for 2 minutes or until thickened.