In a bowl, combine the ground chicken, Greek seasoning, salt, pepper, and garlic. Mix until a smooth paste forms.
Lay the pita breads flat and evenly smash the chicken mixture onto one side of each pita.
Heat a large skillet over medium-high heat and lightly spray with avocado oil.
Place the pita chicken-side down into the hot skillet. Cook for 3–4 minutes, or until the chicken is fully cooked and reaches 165°F.
Flip and cook the pita side for 30 seconds to 1 minute, just until lightly crisped.
Transfer cooked tacos to an oven-safe plate and keep warm in a low oven while finishing the remaining tacos.
Top with tomatoes, red onion, cucumber, dill, feta, and tzatziki. Fold and serve.