For the zucchini soup, bring the soup to a boil, add zucchini, cook until soft, let cool and puree.
Stir in herbs, garlic, oil, lemon juice, pepper and chill for 2 hours and serve. Mix yogurt with a little salt and add one tablespoon yogurt per plate.
Lightly stir apart a bit with a toothpick, leaving marbling visible. Serve the zucchini soup garnished with basil.