In a large pot over medium-high heat, add the butter and olive oil. Add in the onion, garlic, carrots, and celery and saute for about 4-5 minutes, until tender and fragrant. Stir in the zucchini and red pepper and cook for another 2 minutes until slightly softened. Sprinkle in the flour to create a roux and cook for another minute. Slowly add 1 cup of the chicken broth while continuously stirring until it starts to thicken and comes together. Then slowly pour in the remaining chicken broth.