1. Preheat oven to 350°.
2. Arrange pita wedges in a single layer on a baking sheet; lightly coat with cooking spray. Sprinkle pita evenly with za'atar and 1/4 teaspoon salt. Bake at 350° for 15 minutes or until crisp and golden. Cool and break into 1-inch pieces.
3. Combine remaining 1/4 teaspoon salt and garlic on a dry surface. Mash with the side of a knife to form a paste. Combine garlic mixture, juice, and sumac in a large bowl; stir with a whisk. Slowly whisk in olive oil. Add cucumber and remaining ingredients to bowl; toss well to coat. Let stand 10 minutes. Add pita pieces; toss well to coat. Serve immediately.