Begin by preheating your oven to 375°F. Carefully cut the tops off the bell peppers, removing the seeds inside. Arrange the peppers on a lightly oiled baking tray, sprinkle them with salt and pepper, and set them aside.
In a large skillet, heat olive oil over medium-high heat for a couple of minutes until it begins to sizzle. Add the ground beef, stirring frequently, and cook for about 6-8 minutes until the meat is fully browned. Make sure to break the beef into small pieces as it cooks to ensure even browning.
Once the beef is browned, add the diced onion, minced garlic, zucchini, and parsley to the skillet. Sauté the mixture for another 1-2 minutes, allowing the vegetables to soften slightly.
Season the beef and vegetables with salt and pepper, then stir in the soy sauce and tomato sauce. Let the mixture simmer gently for around 3 minutes, stirring occasionally to allow the flavors to meld together.
Next, fold in the cooked white rice and ½ cup of the shredded cheddar cheese. Mix everything thoroughly and remove the skillet from heat.
Stuff each of the prepared bell peppers with the beef and rice filling, then top them with the remaining cheddar cheese.
Place the stuffed peppers in the oven and bake for 40-45 minutes, or until the peppers are tender and the cheese has melted into a golden, bubbly topping. Allow the peppers to rest for 5 minutes before serving. Garnish with additional fresh parsley if desired, and enjoy!