Wash and chop all vegetables. Dice the onion and mince the garlic. Cut the bell peppers, zucchini, and eggplant into bite-sized cubes.

In a large pot, heat olive oil over medium heat. Add onion and sauté for 5-7 minutes. Stir in garlic and cook for 1 minute, then add bell peppers. Sauté for another 5 minutes, followed by zucchini and eggplant for 5-7 more minutes.

Add crushed tomatoes, tomato sauce, and vegetable broth to the pot. Sprinkle in oregano, basil, thyme, and red pepper flakes. Stir well, bring to a simmer, cover, and cook for at least 30 minutes.

Taste and adjust salt and pepper accordingly. For a creamier texture, blend part of the soup. Ladle into bowls, garnish with basil leaves, and serve with crusty bread.