Transfer the thickened yogurt to a large bowl. Squeeze as much liquid from the cucumber as you can and add the cucumber to the yogurt. Mix in the sour cream, vinegar, lemon juice, olive oil, garlic, dill, 1/2 teaspoon salt, and pepper. You can serve it immediately, but I prefer to allow the tzatziki to sit in the refrigerator for a few hours for the flavors to blend.