Hi Murali,
I have not solved this problem ... sorry
But i have used a workaround with : SXPG_COMMAND_EXECUTE (function module).
I run a command (Unix, ...) to unzip from my ABAP code.
More information : Creation of External Commands with the help of UNIX Coding in SAP - ABAP Development - SCN Wiki
Hope it will help you,
Youri