Cook the filling: Brown the ground beef, onion, and garlic in a large skillet over medium-high heat. Drain off any excess grease.
Add spices and vegetables: Stir in the paprika, cumin, oregano, onion powder, parsley, and basil. Add the diced tomatoes, tomato paste, zucchini, Worcestershire sauce, and rice. Bring to a boil, then reduce heat and simmer, covered, for 10 minutes.
Prepare the peppers: Preheat oven to 400°F (200°C). Cut the bell peppers in half lengthwise, remove the seeds and ribs, and place them skin-side down in a baking dish.
Assemble and bake: Fill the pepper halves with the beef and rice mixture. Top with tomato sauce, mozzarella, and cheddar cheese. Cover loosely with foil.
Bake: Bake for 30 minutes, then remove the foil and bake for an additional 15 minutes, or until the cheese is melted and bubbly.
