I have a Z710i and I did not manipulate cmz_config.xml. I used the db2020 no-bruteforce hack http://se-tuning.cz/viewtopic.php?t=3446 and just uploaded the customize_upgrade.xml to the phone via bruteforcing. Now I can make changes through default_upgrade.xml in the accessible part of the filesystem. Did you use the correct customize_upgrade.xml for your phone (the one with source="usb/other...")? You do not need to touch cmz_config.xml at all.