Rinse and slice the zucchini into 1/8-inch strips (about 3 mm) using a knife, mandolin, or vegetable peeler.
Spread the zucchini out on a clean kitchen towel, and generously sprinkle with salt. Let rest for 10 minutes to allow salt to draw moisture out of zucchini.
Pat the zucchini dry with a clean towel and set aside.
Make the Meat Sauce
In a large skillet, over medium heat, add the olive oil and sauté the onion until it is tender.
Add the garlic and sausage and cook it until the sausage is no longer pink.
Reserve about 1/2 cup of the tomato sauce, and add the rest to the skillet. Add salt and pepper to taste. Reduce the heat to low and simmer sauce for 15 minutes or longer.
Mix the Cheese
In a medium sized bowl, combine ricotta, about half the mozzarella, Parmesan, and eggs.
Reserve about 2 tablespoons of parsley to sprinkle on top of the lasagna, and add the rest to the bowl. Mix well and set aside.
Assemble the Lasagna
Preheat oven to 350°F.
Spoon the reserved 1/2-cup tomato sauce into a 9 x 13 lasagna pan and spread to cover the bottom.
Layer the sliced zucchini over the sauce overlapping the edges slightly.
Layer the cheese mixture, and follow with a layer meat sauce. Repeat layering until the pan is full.
Top with remaining mozzarella cheese and sprinkle with the reserved parsley.
Cover the pan tightly with foil and bake for 45 minutes. Then uncover and bake for an additional 15 minutes, or until bubbly.
Remove the zucchini lasagna from the oven and let it stand for 15 minutes to set before cutting. Serve and enjoy. Store leftovers in the refrigerator for up to 4-days or freeze for longer.
Notes
How to Freeze Zucchini Lasagna: Prepare and cook the zucchini lasagna as described above. Once the lasagna has cooled, cut and place into freezer containers or freezer zipper bags. Freeze for up to 3 months.Bake from Frozen: Remove the lasagna from the freezer container and place into a metal baking dish. (Don't use glass or ceramic pans. These may shatter from thermal shock.) Cover the pan tightly with foil and bake for 60 minutes, and then uncover and bake for an additional 15 minutes, or until bubbly. Let it stand for 15 minutes to set before cutting.Thaw Overnight: Thaw the frozen zucchini lasagna in the refrigerator before warming. Remove the lasagna from the freezer container and place it in a metal baking dish, cover with foil, and thaw overnight. Bake in a 350˚F preheated oven for 30-40 minutes, or until heated through. Let it stand for 15 minutes to set before cutting.