In a medium-sized mixing bowl, whisk the feta, water, 1/2 of the cumin, 1/2 of the za’atar spice, and lemon zest together. Set aside.

In a large skillet, over medium-high heat add the lamb, the remaining cumin, remaining za’atar spice, and salt to taste. Cook until the lamb begins to brown, about 5 to 7 minutes. Carefully drain the lamb in a colander, reserving 1 tablespoon of fat in the skillet, and set the lamb aside.

In the same skillet, over medium-high heat, toast the pitas for about 1 minute on one side. Flip the pitas and top with one-quarter of the feta mixture. Cook for about 2-3 minutes until the cheese mixture warms through and begins to melt.

Plate each pita and top with one-quarter cooked lamb, olives, onion, arugula, and drizzle with tzatziki sauce. Fold together and enjoy.