In a large soup pot, heat oil and cook pancetta until browned, about 3 minutes. Add onions, carrots, tomatoes, and zucchini, and sauté for 5 minutes. Stir in garlic and cook for another minute. Add tomato paste, chicken broth, beans, oregano, thyme, and bay leaf to the pot, and bring to a boil. Simmer for 20 minutes.