Put a pot on the stove over medium-low heat; add olive oil and onions to the pot. Season with a little salt and pepper and sauté until translucent; about 10-12 minutes, stirring occasionally. Add garlic and stir for 1-2 minutes.
Meanwhile, cut the zucchini in ½ lengthwise and then slice into ½ moons. Add the zucchini to the pot, season with salt and pepper and stir. Cover the pot, leaving the lid on a tilt and sauté for about 20 minutes, stirring occasionally.
Add the stock, wine and water to the pot. Bring to a simmer; simmer for 5-10 minutes.
Use an immersion blender to puree the soup.
Taste and adjust seasonings if necessary.