Preheat the oven to 400°F (200°C). Line a rimmed baking pan with parchment paper and set aside.
In a large bowl combine the ground chicken, minced garlic, crumbled feta, panko, minced parsley, dill, mint, lemon zest, dried oregano, kosher salt, and black pepper.
Mix the ingredients with your hands or a spoon until evenly combined and the mixture holds together.
Form the mixture into 16 evenly sized meatballs (about 1 to 1 1/4 inches each) and place them on the prepared baking pan, spaced slightly apart.
Bake for 20–25 minutes until the meatballs are cooked through, firm to the touch, and slightly browned.
Warm the pita if needed, then place 4 meatballs in each pita. Top with thinly sliced red onion, cucumber, mixed greens, and tzatziki. Add extra crumbled feta if desired.