In a cast iron skillet, heat the olive oil over medium-high heat. Add the ground beef and garlic. Use a wooden spoon to break up the ground beef while it cooks. Stir occasionally, and cook for about 7 minutes until the meat is no longer pink. Remove the meat from the pan, and set aside.
Add the onions, red bell peppers to the same skillet, and cook for 3-4 minutes or until the onions are soft. If necessary, add a little bit of olive oil to help sauté the veggies.
Add the sweet potatoes and beef broth. Cook for 5-6 minutes. Put a lid on the skillet. The steam will help cook the sweet potatoes faster. Stir occasionally.
Add the zucchini, and cook for 3 minutes.
Return the ground beef to the skillet, and mix everything together.
Add the Dijon, tomato passata, oregano, crushed red pepper, salt, and pepper to taste. Cook for 1-2 minutes more.
Garnish with fresh parsley.