i din undrstand wat u mean by patching and using firmware files...
patching with VKP files? OR unlocking Z500i?
i did it
flashing - successful
patching - successful
customizing - successful
patches - successful

mine is z500i DB2010 CID49 RED, S_ASIAN_LEVAN
i think same as urs.
plz post ur prob in detail. i 'll c hw cn i help

Regards...