Cook the rice noodles according to the directions on the package. Drain well then set aside.
Heat the oil in a non-stick pan over medium-high heat. Add the zucchini, carrots, and mushrooms. Sauté for 3 minutes. Add the ginger, garlic, steak, and half of the scallions. Sauté until the steak is no longer pink. Season with salt and pepper. Stir in the cornstarch.
Add the broth, soy sauce, vinegar, and sugar to the pan.
Simmer for 3-5 minutes, until the liquid thickens. Toss with the noodles. Garnish with scallions.