Preheat the oven to 400 degrees F (200 degrees C). Remove pie crust from the freezer.
Heat a large skillet over medium-high heat. Add sausage. Cook, breaking up the sausage, until juices are released, about 3 minutes. Add red onion, red bell pepper, and garlic; cook and stir until sausage is browned and crumbly, about 5 minutes more. Drain and discard grease.
Combine ricotta cheese, 1/2 cup mozzarella cheese, pesto, Romano cheese, lime juice, Italian seasoning, garlic powder, onion powder, salt, and lemon pepper in a small bowl. Spread over the pie crust. Sprinkle the sausage mixture over the cheese mixture. Arrange zucchini and walnuts on top. Sprinkle with remaining mozzarella cheese.
Bake in the preheated oven until crust is browned, about 30 minutes.