Combine water and cornstarch in a bowl; stir with a whisk. Stir in broth and next 6 ingredients (broth through crushed red pepper).
Heat 2 teaspoons of vegetable oil in a large nonstick skillet over medium-high heat. Add tofu; stir-fry 8 minutes or until golden brown, stirring occasionally. Remove tofu from pan. Place tofu on several layers of paper towels.
Add 1 teaspoon vegetable oil to pan. Add onion and bell pepper, and stir-fry 2 minutes. Add the zucchini, snow peas, carrot, and water chestnuts; stir-fry 1 minute. Add tofu and broth mixture. Bring to a boil, and cook 2 minutes. Stir in cilantro. Serve with rice.