Make the tzatziki sauce by grating the cucumber and placing it in a clean kitchen towel. Twist firmly to squeeze out all moisture. In a small bowl, mix the dried cucumber with Greek yogurt, minced garlic, lemon juice, fresh dill, salt, and pepper. The sauce should be thick and creamy. Set aside.

Preheat your oven to 400°F (200°C) and place flatbreads on a baking sheet. For extra crispiness, brush each flatbread lightly with about 1 tablespoon of olive oil.

In a medium bowl, combine the cooked chicken with 2 tablespoons olive oil, oregano, garlic powder, and lemon zest. Mix thoroughly until the chicken is evenly coated.

Spread the seasoned chicken mixture evenly over both flatbreads, leaving about a half-inch border around the edges.

Bake for 8-10 minutes until the flatbreads turn golden at the edges and the chicken is heated through and steaming hot. Watch closely after 8 minutes to avoid over-browning.

Remove the flatbreads from the oven and immediately top with diced cucumber, red onion slices, cherry tomatoes, Kalamata olives, and crumbled feta cheese.

Drizzle generously with tzatziki sauce (about 3-4 tablespoons per flatbread), sprinkle with fresh dill, cut into wedges, and serve immediately while the flatbread is still warm and crispy.