In a pot over medium, heat the olive oil and add the onion and leeks. Cook, stirring occasionally, until softened, about 3 minutes. Add the celery, carrots, garlic and oregano, and cook until the vegetables are beginning to soften, about 3 minutes more.

Add the zucchini and cook until it begins to soften, about 3 minutes. Add the tomatoes and their liquid and the tomato paste, bring to a boil and cook 3 minutes.

Add the broth, bay leaf and the Parmesan rind. Bring to a boil. Reduce the heat to medium-low. Simmer until the flavours are blended, about 1 hour.

Stir in the beans and kale and cook until tender, about 5 minutes. Remove the rind and serve in soup bowls.