Make Soup:

1.  Heat 3 tablespoons oil over medium high heat in a large heavy Dutch oven. Add onion and salt and cook, stirring often until the onions are starting to brown, 6 to 8 minutes. Add in garlic, and cook, stirring until fragrant but not burning, about 1 minute.
2. Add in white wine, increase heat to high and bring to a simmer. Cook until most of the liquid has evaporated, about 90 seconds. Add in broth and sliced zucchini, cover and bring to a simmer. Reduce heat to medium-low and simmer, stirring occasionally until the zucchini is very tender, about 8 to 10minutes.
3. Transfer half of the soup to a large blender. Use caution when blending hot liquids! Puree until creamy and smooth, about 20 seconds. Transfer to another pot or bowl. Repeat by pureeing the remaining zucchini mixture. Alternatively puree with an immersion blender.
4. Whisk yogurt into the zucchini soup along with 1 tablespoon dill and basil.

Make topping:

1. Heat 1 tablespoon oil in a medium skillet over medium-high heat. Add corn and finely diced zucchini and cook, stirring often until the zucchini and corn is tender, 3 to 5 minutes. Stir in scallion, and remove the skillet from the heat.
2. Ladle the soup into bowls. Drizzle with additional oil and top with several spoonfuls of the topping. Add on additional dill and basil and sprinkle with pepper and serve.