Using a mandoline or V-slicer, thinly slice each zucchini lengthwise, discarding first strip. Slice up to seeded core. Place slices in a medium bowl.
Cut cucumber, onion, ½ of the mint, and lemon peel and add to the bowl.
Whisk together lemon juice and pistachio oil in a small bowl, then pour over zucchini mixture. Toss to coat. Season with salt and pepper.
Cover zucchini mixture and refrigerate for 1-3 hours. When ready to serve, sprinkle remaining mint over the salad, and toss to coat.