In a stockpot, combine the first eight ingredients; cover with water. Bring to a boil. Reduce heat; simmer, covered, 3 to 4 hours or until meat and beans are tender.
Remove pork; cool slightly. Stir carrots, celery and tomatoes into bean mixture; return to a boil. Reduce heat; simmer, covered, until vegetables are crisp-tender. Add zucchini; cook 8-10 minutes longer or until crisp-tender.
Meanwhile, remove pork from bone; discard bone. Cut pork into bite-size pieces; return to pot and heat through. Serve with tortillas. Yield: 16 servings (4 quarts).