In a mixing bowl, combine ground beef, uncooked rice, egg, minced garlic, chopped cilantro, salt, and black pepper. Mix well and form into small meatballs.
In a large pot, heat a bit of oil over medium heat. Add chopped onion and minced garlic, and sauté until softened.
Add chicken broth, sliced carrots, sliced zucchini, diced tomatoes, ground cumin, dried oregano, salt, and black pepper. Bring to a boil.
Carefully add the meatballs to the boiling soup. Reduce heat and let it simmer for about 30 minutes, or until the meatballs and rice are cooked through.
Serve hot, garnished with additional chopped cilantro if desired.