Heat the olive oil in a large pot over medium heat.
Add the diced onion and sauté for 5 minutes until soft.
Stir in the minced garlic and cook for another 1-2 minutes until fragrant.
Add the diced zucchini and stir for another 5 minutes.
Pour in the vegetable broth and bring to a boil.
Reduce the heat and let the soup simmer for 15 minutes.
Add the fresh basil leaves and blend the soup until smooth.
Taste and season with salt and pepper as needed.
Serve immediately, garnishing with extra basil if desired.