In Dutch oven or large saucepan, combine ground beef, salt and pepper; cook over medium-high heat until beef is browned and thoroughly cooked. Drain.
Add carrots, potatoes, onion and broth. Bring to a boil. Reduce heat; cover and simmer 15 to 20 minutes or until vegetables are almost tender.
Stir in zucchini, tomatoes, mushrooms, thyme and Worcestershire sauce. Cook 5 to 10 minutes or until zucchini is tender.
In small jar with tight-fitting lid, combine water and flour; shake well to blend. Gradually add to stew, stirring constantly; cook and stir until bubbly and thickened.