the last update ever for the Zio is 2.2...you can try flashing a new ROM.  If u want to change ur android version ( wont  change the version just how it looks  in settings...mines running 2.2  but under settings i made mine say 4.0)  Go into ur root explorer (mines ES File Manager) go to system and open build.prop  go down to androidversion=2.2 and put 2.3.3 or whatever (it may say something diffrent from androidversion but its something close to that).  Reboot and go to settings\aboutphone and scroll down to android version and it'll be changed