Combine first 6 ingredients; add 1 teaspoon rind, stirring well. Divide mixture into 8 equal portions, shaping each into 1/4-inch-thick oval patties.
Heat oil in a large nonstick skillet over medium-high heat. Add patties; cook 2 minutes on each side or until browned. Cover, reduce heat to medium, and cook 4 minutes.
Combine remaining 1 teaspoon rind, yogurt, and oregano, stirring well. Fill each pita half with 1 patty, 1 tablespoon yogurt mixture, 1/4 cup lettuce, and 1 tablespoon tomato.