If you've never changed the partition then just leave it alone and flash OZ.
If you have changed the partition sizes, then use the same tools you did previously (i.e. the cacko or pdaXrom updater.sh and tools.tar) but just don't flash the cacko/pdaXrom image.
NB. Make sure you use the OZ updater.sh, not the cacko/pdaXrom one, when you come to flash the OZ image.
Si