Slice the peeled cucumbers into ½-inch circles. Place on a serving platter or tray.
In a blender, combine the feta cheese, yogurt, garlic, and dill. Blend until smooth, adding a dash of water as needed to promote blending. Pour the whipped feta into a plastic bag. Seal the bag and use scissors to cut off a small piece from one of the bag's bottom corners. This will create a makeshift piping bag. Squeeze a small amount of the whipped feta onto each cucumber slice.
Garnish the canapes with fresh lemon zest, black pepper, and sprigs of fresh dill.
You can prep these up to 3 hours in advance. Cover with plastic wrap and store in the fridge until you plan to serve them.