In a large pot over medium heat, add in ground sausage and ground beef. Use a spoon to break up the meat into small pieces. Add in onion and garlic and cook until meat is well browned, stirring constantly. Stir in sugar, fresh basil, fennel, oregano, 1/2 teaspoon salt, pepper, and 1/4 cup chopped parsley. Pour in crushed tomatoes, tomato paste, tomato sauce, and chicken broth. Stir well and bring to a simmer. Reduce heat to low and simmer until ready to assemble lasagna.
Meanwhile, cut zucchini lengthwise into 1/8-inch thick strips. Place zucchini into a large colander. Sprinkle with salt to draw out moisture. Rinse and pat dry.
In a mixing bowl, combine ricotta cheese with egg, parsley, 1/2 teaspoon salt, and nutmeg. Refrigerate until ready to assemble lasagna.
Preheat oven to 375 degrees. Lightly grease a deep 9x13 pan.
To assemble, spread about 1 cup of meat sauce in the bottom of the prepared pan. Place a layer zucchini noodles on top to cover the bottom of the pan. Spread with 1/3 of the ricotta cheese mixture. Top with 1/4 of mozzarella cheese. Spoon 1 1/2 cups meat sauce over mozzarella, then sprinkle with 1/4 cup parmesan cheese. Repeat layering two more times to create three complete layers. To finish, place a final layer of zucchini, topped with another 1 cup of meat sauce to cover the zucchini. Top with remaining mozzarella and Parmesan cheese. Cover loosely with aluminum foil.
Bake in preheated oven for 50 minutes until cheese is bubbling and browned. Serve hot. Let stand 10 minutes before slicing.