findLeafB u (Black2Zip v l r c)
  | u < v     = findLeafB u $ toBlackZip l (Right $ BlackCrumb v (Right r) c)
  | otherwise = findLeafB u $ toBlackZip r (Right $ BlackCrumb v (Right l) c)
findLeafB u (Black2Zip v l r c)
  | u < v     = findLeafB u $ toBlackZip l (Right $ BlackCrumb v (Right r) c)
  | otherwise = findLeafB u $ toBlackZip r (Right $ BlackCrumb v (Right l) c)
findLeafB u (Black2Zip v l r c)
  | u < v     = findLeafB u $ toBlackZip l (Right $ BlackCrumb v (Right r) c)
  | otherwise = findLeafB u $ toBlackZip r (Right $ BlackCrumb v (Right l) c)