Roughly chop the peeled cucumbers and zucchini into manageable pieces.
In a high-speed blender, combine the cucumbers, zucchini, fresh dill, Greek yogurt, olive oil, lemon juice, garlic, sea salt, and black pepper.
Blend on high speed until the mixture is completely smooth and creamy. If the soup is too thick, add a tablespoon of cold water until it reaches your desired consistency.
Transfer the soup to an airtight container, cover, and refrigerate for at least 2 hours to allow the flavors to meld and chill thoroughly.
Ladle the chilled soup into bowls. Garnish with a drizzle of olive oil, a pinch of black pepper, extra fresh dill, and chili flakes before serving.