Creating Zucchini Tomato Italian Sausage Soup is simple when you follow these easy steps:

1. Brown the Sausage: In a large pot, heat olive oil over medium heat. Add the Italian sausage and cook until browned, breaking it into pieces with a spoon.
2. Cook Onion and Garlic: Add chopped onion and minced garlic to the pot. Sauté for about 3-4 minutes until the onions are translucent.
3. Add Zucchini: Stir in the sliced zucchini and cook for another 5 minutes until slightly softened.
4. Incorporate Tomatoes and Broth: Pour in the diced tomatoes with their juice and the chicken or vegetable broth. Stir well to combine.
5. Season the Soup: Add Italian seasoning, red pepper flakes (if using), salt, and pepper to taste. Bring the mixture to a simmer.
6. Simmer: Allow the soup to simmer for 10-15 minutes until the zucchini is tender and the flavors meld together.
7. Taste and Adjust: Taste the soup and adjust seasoning if necessary before serving.
8. Serve: Ladle the soup into bowls and garnish with fresh basil leaves if desired.

Following these steps will lead you to a delightful and satisfying Zucchini Tomato Italian Sausage Soup!