Combine the olive oil, lemon zest, lemon juice, garlic, cinnamon, salt, black pepper and 2 tablespoons of the Za’atar spice in a glass dish or zipper sealable plastic bag. Add the chicken leg quarters, red onions and sprigs of thyme. Coat all sides of the chicken and rub the marinade into and under the skin. Refrigerate for 4 hours or up to overnight.