In a large pot, heat the oil over moderately low heat. Add the onion and half the jalapenos and cook, stirring occasionally, until the onion is translucent, about 5 minutes. Add the zucchini,1 1/2 teaspoons of the dried oregano, if using, and 1/4 teaspoon of the cumin and cook, stirring, until the zucchini starts to soften, about 3 minutes.

Add the broth, water, tomatoes, 1 1/4 teaspoons of the salt, and 1/2 teaspoon of the black pepper; bring to a simmer. Simmer for 15 minutes.

Meanwhile, in a medium bowl, combine the ground beef, garlic, the remaining jalapeno, 1/4 teaspoon cumin, 3/4 teaspoon dried oregano or 1 tablespoon of the fresh oregano, 1/2 teaspoon salt, and 1/4 teaspoon black pepper, the bread crumbs, and the egg. Shape the mixture into 24 meatballs, about 1 inch in diameter.

Add the meatballs and corn to the soup and simmer until the meatballs are just done, about 5 minutes. Stir in the lime juice and the remaining 1 tablespoon fresh oregano, if using.