EZ4 client is the software that the EZFlash IV uses to add files to the miniSD card. Should you wish do some Translations of the software into your own language open one of the .lng files in the Language subdirectory of the client and edit the text right of the = sign.
It supports .zip and .rar compression formats.
See this article for a usage guide.
Picture of the software (to change skin open the config menu and the options are the lowest ones) http://members.lycos.co.uk/fast6191/screenshotclient.JPG