In a mixing bowl, combine olive oil, lemon juice, minced garlic, oregano, paprika, salt, pepper, and red pepper flakes. Whisk until well blended. Cut the chicken into strips and coat completely in the marinade. Let it sit for at least 15 minutes.

In another bowl, combine diced cucumbers, tomatoes, bell pepper, red onion, and parsley. Drizzle with lemon juice and season with salt and pepper. Stir gently and let sit for 10-15 minutes.

Heat a skillet over medium-high heat. Add the marinated chicken in a single layer and cook for about 3-5 minutes until golden. Flip and cook for another 3-5 minutes until internal temperature reaches 165°F. Let the chicken rest.

Warm the pitas in the skillet or oven at 350°F for about 5 minutes. Assemble the tacos by placing chicken strips in the pitas, topping with fresh salsa, and drizzling with tzatziki.