Whisk together olive oil, lemon juice, red wine vinegar, salt, oregano, pepper and garlic powder. Coat chicken in marinade, cover and refrigerate for 30 minutes. Grill chicken for about 6 minutes on each side, until cooked through.Toss lettuce in some of the dressing. Top with tomatoes, cucumber, radish, red onion, olives, sliced chicken breast and pita chips. Top with more Tzatziki Ranch dressing and crumbled feta.