How to Make It
Preheat broiler to high. Heat a large skillet over medium-high heat. Add oil; swirl to coat. Add mushrooms, garlic, and zucchini; sauté 6 minutes or until tender and mushroom liquid evaporates.
Arrange 2 tortillas on a baking sheet; coat tortillas with cooking spray. Broil 2 minutes or until browned. Place, browned side down, on a work surface. Repeat with other 2 tortillas.
Combine tomato sauce, oregano, and salt in a microwave-safe bowl; microwave at HIGH for 30 seconds. Spoon 2 tablespoons sauce on unbrowned side of each tortilla.
Divide vegetables over tortillas; sprinkle each with about 1/3 cup cheese. Place 2 pizzas on baking sheet. Broil 2 minutes or until cheese melts. Repeat with remaining pizzas.