z85 is a binary string codec, like hexadecimal or base64, but has a higher density of compression than the former, due to its use of a higher base value of 85 than base 64. ByteStrings just need to be a length of a multiple of 4 (a Word32String might be a better name).
There are multiple layers of exposed implementation in this package
Word32 <-> Vector 4 Z85Char
for low level work- Attoparsec
Parser ByteString <-> Parser Text
for slightly higher level parsing of strict data - Pipes
Pipe ByteString Text <-> Pipe Text ByteString
for encoding / decoding streams of strict data - Casual
Lazy.ByteString ~ Lazy.Text
functions for encoding / decoding lazy data.