In a mixing bowl, whisk together olive oil, lemon juice, garlic, oregano, paprika, salt, pepper, and red pepper flakes. Add chicken and marinate for at least 15 minutes.

Chop cucumbers, tomatoes, bell pepper, and red onion. Combine with parsley and feta in a separate bowl. Drizzle with lemon juice and season with salt and pepper. Let sit for 10 minutes.

Heat a skillet over medium-high heat and cook chicken for 3-5 minutes on one side. Flip and cook another 3-4 minutes until cooked through.

Warm pitas over a gas flame or skillet until soft. This enhances the taco experience.

Assemble tacos by placing chicken in each pita, topping with salsa, and drizzling with tzatziki.