Add all the salad dressing ingredients to a container with a lid and shake well. Alternatively, whisk ingredients together in a bowl. Transfer to refrigerator to chill while you make the salad.
Make the salad: Peel and cut the cucumbers in half lengthwise. Optionally, use a spoon to scoop out the seeds. Slice the cucumbers into bite-sized pieces.
Use a sharp knife to all the way around the avocado from top to bottom. *The knife will stop when it reaches the pit. Twist the two halves in opposite directions to open the avocado. Remove and discard the pit, then dice the avocado.
Add all the salad ingredients to a large bowl. Drizzle salad dressing over the top, then use tongs to mix and toss. Season with additional salt and pepper if desired.
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Notes
To make in advance: Assemble all the salad ingredients in a bowl except for the avocado and Greek salad dressing. Keep covered and refrigerated for up to a day. Just before serving, add the avocado, then toss the salad with the dressing.