Place the drained canned chicken in a bowl and gently break up any large chunks with a fork so the pieces are flaky but not mushy.
In a separate medium bowl whisk together the Greek yogurt, mayonnaise, lemon juice, Dijon, garlic powder and Greek seasoning until smooth and slightly glossy.
Toss the diced cucumber, minced red onion, chopped olives and half of the chopped dill with the dressing so the vegetables are evenly coated; this helps keep them crisp.
Fold the flaked chicken into the dressed vegetables, turning gently to avoid breaking up the cucumber or over-mashing the chicken. Taste and adjust seasoning with black pepper.
Transfer to a serving bowl and sprinkle the crumbled feta, remaining dill and chopped parsley over the top for texture and color. For best flavor let the salad rest in the refrigerator for 15–20 minutes before serving.
Serve chilled on a bed of greens, inside a pita, or with crackers. Store leftovers covered in the fridge for up to 3 days.