foldlz :: (b -> Zipper a -> b) -> b -> Zipper a -> b
foldlz f x z
        | endp z    = x
        | otherwise = foldlz f (f x z) (right z)
foldlz :: (b -> Zipper a -> b) -> b -> Zipper a -> b
foldlz f x z
        | endp z    = x
        | otherwise = foldlz f (f x z) (right z)
foldlz f x z
        | endp z    = x
        | otherwise = foldlz f (f x z) (right z)