Open ES File Explorer and go to the Downloads directory, the file should be there, now:
- Long Press the file, and select Copy
- Press the UP button on toolbar until it says "/sdcard/" in the location bar directly above the toolbar
- tap the "ext_sd" folder
- tap the "Paste" button in the toolbar
- Long Press the file and select "Rename"
- Change the name to "PH98IMG.zip" and click OK
Once all that is done, power off the phone, wait for all the buttons to go dark and give it another 15-30 seconds. Now hold down the VOL DOWN and well holding it down, press down and hold the POWER button, continue to hold both buttons until it starts installing then release the buttons. It will take a while and reboot several times by itself, just let it sit, then it should come up and go to the setup screen (if it hasn't after 30 minutes, pull the battery, and power on normally and wait for the setup screen). Once it is up, power off and do the VOL DOWN+Power thing a SECOND TIME, it will go another 20 minutes or so and come up to the setup screen, proceed through the setup and enjoy Ice Cream Sandwich!
Sometimes you have to do the VOL DOWN+Power a few times before it takes, the buttons on the Rezound are tricky.