y x2 // inspection
U R F z' (U' D) R U' z D2 R // cross
U' y' R U' R' U R U R' // 1st pair
R' U' U' R U' R' U' R // 2nd pair
y' R U R' U' R U R' U R U' R' // 3rd pair
y U' y R' U' R U' R' U R // 4th pair
U' U' R' U' R U' R' U' U' R2 U R' U' R' F R y' R' U' U'