Preheat the oven: Preheat your oven to 375°F (190°C).

Prepare the filling: In a skillet over medium heat, cook the ground beef and chopped onion until the beef is browned and fully cooked. Drain excess fat, then season with salt, garlic salt, oregano, parsley, and diced green pepper. Stir and cook for an additional 2-3 minutes until the green pepper softens slightly.

Mix in the breadcrumbs and egg: Remove the skillet from heat. Stir in the bread crumbs, Parmesan cheese, and lightly beaten egg until the mixture is well combined.

Assemble the pie: Roll out half of the pie pastry and fit it into the bottom of a deep-dish pie pan. Layer half of the sliced zucchini on the bottom of the pie crust. Spoon the meat mixture over the zucchini, spreading it evenly. Top with the thinly sliced tomatoes, then layer the remaining zucchini slices over the top.

Cover with the top crust: Roll out the second half of the pastry and place it over the pie. Crimp the edges to seal and cut small slits in the top crust to allow steam to escape during baking.

Bake the pie: Bake the zucchini hamburger pie in the preheated oven for 45-50 minutes or until the crust is golden brown and the zucchini is tender. If the edges of the crust start to brown too quickly, cover them with aluminum foil halfway through baking.

Cool and serve: Allow the pie to cool for 10 minutes before cutting and serving. Enjoy this hearty, flavorful dish with a side salad or on its own for a complete meal.