where are you getting this stock rom file from and how are you trying to 'flash' it? any pure stock file we have for esteem is just a CWM or RZR recovery backup, unless your reffering to ld-lg which is a stock based rom.. but none the less we need more info
im guessing your trying to flash a stock backup which needs to be 'flashed' as a backup-restore, so you want to place it in proper sd directory(unzipped) then flash as 'restore backup' in CWM menu options
i will be glad to provide more info if needed, jest send a pm or re-post here on the thread