Although I havent booted this phone up for years, I still disagree. OpenZio ROM far surpasses the stock ROM in performance, benchmarks and snappiness.
But if you are insistent on returning to stock, try formatting /system in CWM's advanced settings, then flash the backup.
Alternately, you can always run the 2.2.1 update to restore to a completely stock, unrooted system.
http://xdaforums.com/showthread.php?t=966047
The "2.1.x" rom I was quoting in my previous post was the OpenZio rom, and yes it performs extremely well. Just no App to SD ability, among other limitations. Phone runs great with it however. Every other rom ive tried 2.2.x (except stock) seems to be generally very slow, and slow at recognizing screen input (almost a whole second from touching the screen until it actually recognizing there is a touch, which is hard very work with), and the screen's touch input seems to be uncalibrated somewhat. Ill try "formatting /system" then flashing the backup, but I guess the question I should have originally asked was: Do I flash this zip as I would any other custom rom from the SD? (Install Zip from SD>Select this ZIP). Im not familiar with the ZIO as I use T-Mobile, but I assume since its CW Recovery and it would be the same, right?
How do I perform the mentioned: "run the 2.2.1 update to restore to a completely stock, unrooted system."?
If I go to Settings/About/Update it says I need to be on Wifi, which it is (The phone's not activated). Ive tried doing that with every available rom in the forum.
UPDATE:
Just tried this, however when I choose to install this ZIP from SD, it starts to install, and within a half second goes back to the Recovery main screen.
Nothing changes (Except that I formatted everything)