Preheat the oven to 350°F (175°C). Slice the zucchinis into thin 1/8-inch slices using a mandolin or sharp knife.
Arrange the zucchini slices in a single layer on a baking sheet and sprinkle with 1 tablespoon salt. Bake 10–15 minutes until just beginning to brown and released of moisture, then set aside.
Increase oven temperature to 375°F (190°C). In a large skillet over medium-high heat, warm 2 tablespoons olive oil. Add ground turkey, diced onion, 1 1/2 tablespoons minced garlic, 1 teaspoon salt, and a pinch of black pepper. Cook until turkey is browned and onion is soft, about 6–8 minutes.
In a mixing bowl, beat together the 15-ounce ricotta container and 1 large egg; season with a pinch of black pepper and set aside.
Spray a 9×13-inch baking pan with cooking spray. Spread half of the 14-ounce jar of pizza sauce on the bottom of the pan.
Layer half of the cooked turkey over the sauce, then half of the zucchini slices, then half of the ricotta mixture, half the turkey pepperoni slices, and half (4 ounces) of the grated mozzarella.
Repeat the layers: remaining sauce, remaining turkey, remaining zucchini, remaining ricotta mixture, remaining pepperoni, and remaining grated mozzarella. Sprinkle chopped 1/2 green pepper, 1/4 cup slivered black olives, and 2 tablespoons grated Parmesan on top.
Cover the pan with foil and bake at 375°F for 45 minutes. Remove foil and bake uncovered for an additional 10 minutes.
Broil on high for 2–3 minutes until the top is golden and bubbly, watching closely to avoid burning. Let stand 5 minutes before slicing and serving.