In a large pot, combine 1 cup of the herbs, zucchini, green beans, potatoes, tomatoes, onion, pepper flakes, garlic, and 8 cups of cold water. Add salt and bring to a boil over high heat. Reduce heat to medium-low and cook, covered, until the potatoes are tender, 20 to 25 minutes.
Add bread, and cook, stirring, with a wooden spoon, until the bread has broken down and thickened the soup, about 10 minutes. Stir in remaining 1/2 cup herbs; season with salt and pepper.
Ladle soup into bowls and drizzle with olive oil. Serve immediately.