findLeafB u (Black3Zip v l r c)
  | u < v     = findLeafR u . toRedZip l $ BlackCrumb v (Right r) c
  | otherwise = findLeafB u $ toBlackZip r (Right $ BlackCrumb v (Left l) c)
findLeafB u (Black3Zip v l r c)
  | u < v     = findLeafR u . toRedZip l $ BlackCrumb v (Right r) c
  | otherwise = findLeafB u $ toBlackZip r (Right $ BlackCrumb v (Left l) c)
findLeafB u (Black3Zip v l r c)
  | u < v     = findLeafR u . toRedZip l $ BlackCrumb v (Right r) c
  | otherwise = findLeafB u $ toBlackZip r (Right $ BlackCrumb v (Left l) c)