Cut the cucumbers into large chunks. Set aside a few chunks for the garnish. Puree the remaining chunks of cucumber with the yoghurt. Press in the garlic. Add the finely grated lemon zest, squeeze out the juice. Add the lemon juice, salt, pepper and 2/3 of the dill leaves to taste. Cover and refrigerate for approx. 2 hrs. To serve, pour the soup into a large preserving jar.