PREHEAT oven to 375°F. Grease 13 x 9-inch baking dish.
HEAT oil in large skillet over medium-high heat. Add zucchini and peppers; cook, stirring frequently, until soft, for about 8 minutes. Add garlic; cook for an additional 2 minutes. Season with 1/4 teaspoon each salt and pepper. Remove from heat.
MEANWHILE, WHISK together flour, 1/4 cup evaporated milk and remaining 1/4 teaspoon each of salt and black pepper in medium saucepan until smooth. Whisk in remaining evaporated milk. Heat over medium heat, stirring frequently, until mixture comes to a boil. Reduce heat; simmer for 3 minutes or until thickened. Stir 2 cups of milk mixture into cooked vegetables; reserve remaining milk mixture.
SPREAD 1/2 cup marinara sauce over bottom of the prepared baking dish. Top with 3 noodles. Top with half of the vegetable mixture. Top with 3 noodles. Spread 1 cup marinara sauce and sprinkle with 3/4 cup mozzarella cheese. Layer 3 noodles, remaining vegetables and remaining 3 noodles. Top with remaining marinara sauce, reserved milk mixture, remaining 3/4 cup mozzarella cheese and Parmesan cheese.
BAKE for 35 to 40 minutes until golden and bubbly on the edges. Let stand for 10 minutes before serving.
• For extra flavor, add a bay leaf to the white sauce while cooking.