Current definion of (<|>) for ZipLists:

ZipList xs <|> ZipList ys = ZipList (xs ++ drop (length xs) ys)

doesn't work if the left argument is infinite. It should be:

ZipList []     <|> ys             = ys
xs             <|> ZipList []     = xs
ZipList (x:xs) <|> ZipList (_:ys) = ZipList (x : (ZipList xs <|> ZipList ys))