x y2 // inspection
R U z' R' U y' R' z R' D // cross
U' U' R' U R // 1st pair
U R U' R' z U R' U' // 2nd pair
z' y' U' U U' R' U R U' R' U R // 3rd pair
U' U' R U' R' U' U' R U' R' // 4th pair
U R' U' U R U' // error
U' R U R' z U' R' R' z' R U R' z R U R' U' R2 U