Using a grater, grate one whole english cucumber, sprinkle with a tsp of salt, toss and then place in a colander and set aside for 20-30 minutes (you want the extra liquid from the cucumber to drain before adding to the yogurt. The salt will help. It doesn't have to be completely dry, you just don't want all of the excess liquid. You can give the cucumbers a "gentle" press to help guide some of the moisture out as well).
Meanwhile, in a bowl add the greek yogurt, garlic, the zest and juice of one lemon, dill, and sprinkle with salt and pepper. Add drained cucumbers. Gently mix together.
Transfer to a serving bowl and drizzle with olive oil and garnish with additional dill.