MMDZip is a very useful program developed in the chinese MMD fanbase
http://www.moe5.net/forum.php?mod=viewthread&tid=3065
Software link
http://pan.baidu.com/share/link?shareid=3848&uk=3693961335
What is does:
MMDZip is basically a combo of Applocale and 7zip .It allows de-compression with the kana names kept. Moreover, if a zip contains a japanese password, it offers the ability to convert the password as well, making the extraction much easier and with less headaches xD.
You have to use this software, trust me :D