In a large skillet over medium high heat add the olive oil and onion. Sauté until tender and add the ground beef and sausage. Cook and crumble until brown and cooked throughout. Add crushed tomatoes, tomato sauce, tomato paste, Italian seasoning, sugar, and basil. Let simmer on low heat.
In medium sized bowl add the ricotta cheese, parmesan, and egg. Mix until incorporated.
Preheat oven to 375 degrees and spray a 9x13 inch pan with non stick spray and set aside.
To make the lasagna start by spreading 1 cup of the meat sauce on the bottom. Arrange the zucchini slices in a single layer over the meat sauce. Spread 1/2 cup of the ricotta cheese, on top of the zucchini followed by shredded mozzarella cheese. Repeat the layers and top with cheese.
Cover with aluminum foil and bake for 20 minutes. Remove the foil and bake and additional 20-25 minutes or until it is heated throughout and cheese is bubbly. Let it cool for 10 minutes before serving.