In a large Dutch oven, combine squashes, mushrooms, onion, and bell pepper with enough water to cover. Bring to a boil over high heat. Reduce heat to medium, and simmer for 5 minutes, or until vegetables are tender. Drain vegetables well and return to Dutch oven.

Add diced tomatoes, tomato paste, garlic, sugar, salt, and pepper. Bring to a simmer over medium heat and cook for 20 minutes.

In a medium bowl, combine ricotta cheese, cream cheese, and eggs; set aside.

Preheat oven to 350 degrees F. Grease a 14 1/2-x-11-inch baking dish.

Spread half of sauce mixture in the bottom of prepared baking dish. Place 3 uncooked lasagna noodles on top of sauce. (Do not overlap noodles.) Spread half of ricotta mixture over noodles. Place 6 slices of mozzarella cheese on top of ricotta mixture. Top with 2 cups Italian cheese blend. Repeat layers, using remaining sauce, noodles, ricotta mixture, mozzarella, and Italian cheese blend.

Bake for 40 minutes, or until hot and bubbly. Let stand for 10 minutes before serving.