Heat the oil and saute the onion for 5 minutes.
Combine tomatoes, zucchini, potatoes and garlic cook at medium heat for 10 minutes.
Pour the stock into the pan and bring the soup to a boil.
Once at a boil, cover and lower temperature simmer. Cook until vegetables are tender.
Remove from the heat and stir in basil. Add salt and pepper to taste.
Serve hot.