In a large bowl, combine the ground beef, diced onion, minced garlic, cooked rice, beaten egg, chopped cilantro, cumin, oregano, salt, and pepper. Mix well and form into 1-1.5 inch meatballs.

Heat olive oil in a large skillet over medium heat. Brown the meatballs in batches, then set aside.

In a large pot, sauté the diced onion and minced garlic until soft and fragrant (about 5 minutes).

Add the beef broth, diced tomatoes, cumin, oregano, salt, and pepper. Bring to a simmer.

Carefully add the browned meatballs, potatoes, carrots, and zucchini to the pot. Stir gently.

Cover and simmer for 30-35 minutes, or until the vegetables are tender and the meatballs are cooked through. Adjust seasoning to taste.

Ladle into bowls and garnish with extra cilantro, if desired. Serve hot.