In a medium bowl, combine ground beef, basil, oregano, and garlic.
Make 1-inch meatballs until all of the meat is used, and place in bottom of slow cooker.
In a large bowl, combine tomato sauce, broth, onion, bell pepper, leeks, garlic, salt, pepper and basil. Pour over meatballs.
Cover and cook on LOW for 8 hours.
Turn heat to high and add zucchini, stirring well, then recover and cook for another 15-20 minutes, until zucchini is tender-crisp.
Serve immediately and enjoy!