Add water to a large pot (about 6-8 qt). Add beef shanks and simmer over medium heat for about 2 hours, until meat is falling apart and the broth is very rich. Add salt and pepper
Now, add corn, potatoes, carrots, onion and chayotes. Let it simmer for 10-15 minutes, then add zucchinis and cabbage. Let it cook for another10-15 minutes, until very tender.
Serve with fresh chopped cilantro, sliced avocado , sliced jalapenos and a dollop of sour cream (optional)