In a large saucepan with a tight-fitting lid, heat the olive oil over medium heat until hot. Add onion, carrots and celery; saute for 7 minutes.
Add zucchini, salt and pepper; saute for 5 minutes. Add broth; bring mixture to a boil then reduce heat, cover and simmer for 10 minutes.
Add basil; simmer for 4 minutes. Transfer soup to a food processor or blender and puree until smooth. Serve garnished with cheese.