Chop the leek and wash the pieces in a bowl of cold water, agitating it. Allow any dirt or grit to settle, then lift out the leek pieces and and pat dry. Pull the leaves from the parsley stems and set aside. Coarsely chop the stems. Peel the zucchini if desired and cut into 1/2-inch cubes.Cook parsley stems and leek in oil in a 2- to 3-quart heavy saucepan over moderately low heat, stirring occasionally, until softened, about 5 minutes. Add zucchini and salt and cook, stirring, 1 minute. Add wine, if using, and water. Simmer, covered, until zucchini is very tender, about 10 minutes.Puree mixture in a blender with parsley leaves until smooth. If not using wine, add soy or tamari sauce to taste. Season with salt and pepper. Reheat if necessary.IMPORTANT! Always use great caution when pureeing hot liquids. If you have time, allow the soup to cool before blending. Never fill the container more than half full and cover the lid with a folded kitchen towel and hold it in place before you turn on the blender. The initial surge of the blender's contents can cause the lid to pop open, possibly scalding you if still hot and certainly making a mess of your kitchen.