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.
Notes
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.