In a large - 8 quarts or more) stockpot, combine the broth, oregano, onions and chile and bring to a boil; reduce heat to low and simmer.
Add carrots, rice or potatoes, cilantro and zucchini if using. Simmer, uncovered 10 to 15 minutes until tender.
While that is simmering, combine the beef, breadcrumbs and eggs and shape mixture into small balls no larger than 1 1/2 inches in diameter.
Drop meatballs into soup. Simmer uncovered about 5 minutes.
Spoon off any fat and/or foam from surface of soup. Add the chiffonaded spinach to the soup and cook 5 another five minutes.
Ladle the soup into bowls and pass with the lime wedges to squeeze over soup or float on top.Servings: 6 to 8