.gz 과 .zip 은 다르다.

발췌, http://zlib.net/manual.html 

The library also supports reading and writing files in gzip (.gz) format

  with an interface similar to that of stdio using the functions that start

  with "gz".  The gzip format is different from the zlib format.  gzip is a

  gzip wrapper, documented in RFC 1952, wrapped around a deflate stream.

     This library can optionally read and write gzip streams in memory as well.

나만 헤깔렸던 포맷.
.gz 와 .zip은 다르다.
예전까지 아무생각 없이 둘은 같은줄 알았다.
이름 때문이었나? 아 쪽팔려 ==3=3=3