Place Mushrooms And Chicken In A Slow Cooker. Add The Celery, Zucchini, Carrots, Onion, Tomato Juice, Broth, Garlic, Paprika And Pepper. Cover And Cook On Low For 5 Hours Or Until Meat Juices Run Clear. Remove Chicken And Vegetables And Keep Warm. Transfer Cooking Juices To A Saucepan; Skim Fat. Combine The Cornstarch And Water Until Smooth; Add To The Juices. Bring To A Boil; Cook And Stir For 2 Minutes Or Until Thickened. Pour Over Chicken And Vegetables; Serve Over Rice.