This sausage and zucchini soup works great in the slow cooker. Start by sauteing the sausage, onion, garlic, celery, and bell peppers in a skillet until the sausage is cooked through. Add that sausage to the slow cooker with the broth, diced tomatoes, and herbs. Cook on low for 4 hours. Add the zucchini to the slow cooker during the last 15 minutes of cooking so it doesn't get mushy. Season and serve.