This lasagna will freeze well so you can divide it into 2- 8x8” pans and freeze one for later use or you can double the ingredients and make two pans, using one for tonight’s meal and freezing one for later use.
On a parchment lined cookie sheet, line prepared zucchini slices in a single layer and sprink lightly with salt. Bake for 10 minutes, turning once half way through bake time. Remove zucchini from oven; reduce oven temperature to 375°F.
Combine cooked ground beef, onion, broccoli, cauliflower, spinach, garlic, salt, and pepper in a large skillet and sauté for about five minutes. Add spaghetti sauce to meat/vegetable mixture and simmer for 10 minutes, stirring occasionally.
In a lightly sprayed 9x13" baking dish, assemble lasagna as follows: layer 1/3 of sauce mixture followed by a layer of 1/3 of zucchini, a layer of ½ of the ricotta, a layer of 1/3 of the Parmesan, and a layer of 1/3 of the mozzarella. Repeat all layers: 1/3 of meat, 1/3 of zucchini, remainder of ricotta, 1/3 of Parmesan, and 1/3 of Mozzarella. For final layer, use remainder of sauce mix, remainder of zucchini, and the rest of the Parmesan and mozzarella cheeses.
Cover with foil and bake 45 minutes. Remove foil and bake 10 minutes longer. Remove from oven and let sit for 10 minutes before serving.