Preheat oven to 350, grease a 9 x 13" baking pan with pan spray, set aside.
Place a single layer of zucchini slices in the pan, overlapping the edges SLIGHTLY.
Gently spread ⅓ of the sauce over the noodles, scatter 1 cup of the mozzarella over the sauce.
Add another layer of zucchini, blotting with paper towels as you go.
Gently spread ½ of the ricotta filling, followed by another layer of zucchini. Place some paper towels over the surface, and gently press down to compress. Discard paper towels.
Spread another ⅓ of the sauce, then another cup of the mozzarella. Top with another layer of zucchini, again blotting and compressing.
Spread remaining ricotta , followed by the last layer of zucchini. Compress, then top with remaining sauce.
Scatter remaining mozzarella over the top, as well as the Parmesan cheese.
Bake uncovered for 45 minutes, or until the cheese is golden brown and bubbly.
Remove baked lasagna from the oven and allow to rest for 10-15 minutes before cutting and serving.