If the problem was already solved, my bad, sorry I missed it.First the problem was already solved, see The Halo's latest post. Second although mostly technically true, this statement isn't true in general.
All depend on the used compression algorithm and the data itself. Most time you won't end with that and only get sightly better compression, but I wouldn't general write that you can't compress a already compressed file to 41% of it size.
About the compression, see my previous reply.
We were talking about RAR-ring a ZIP, so of course about LOSSLESS compression.
You can't compress a zip "loosing quality"