In a large mixing bowl, whisk together olive oil, lemon juice and zest, minced garlic, oregano, paprika, salt, and pepper. Add chicken and marinate for 15-45 minutes.

Chop cucumber, cherry tomatoes, red bell pepper, and red onion into small pieces. Combine in a bowl with parsley, feta cheese, and lemon juice. Season with salt and pepper.

Heat a non-stick skillet over medium-high heat. Cook marinated chicken for 3-5 minutes on one side until golden brown, then flip and cook for another 3-4 minutes until fully cooked.

Warm whole wheat pitas on a griddle for 1-2 minutes. Layer in cooked chicken, cucumber tomato salsa, and tzatziki to assemble the tacos.