I believe you would have to unpack the system blob for that and that's way over my head....
On the Asus download site, they provide the T4_SDupdate file only for WW SKU. All the other SKUs have only one firmware file version. And the update instructions for the T4 version are different too. This version seems to be designed to be used from your microSD versus the other ones from your internal. I wonder if that is because Asus pushed out an incompatible update to WW users which was only recoverable by wiping data from the bootloader and reflashing the firmware from the microSD...
None of that helps you though...
If you done everything correctly: Downloaded the CN firmware twice (just to make sure your problem is not simply a corrupted download), extracted the downloaded file once and you are unable to flash that file in CWM we may be dealing with a new situation here...Namely CWM not being capable of flashing a firmware zip.....
If all of the above is true, the only way I know of to get the latest bootloader on your tablet would be to flash the system blob in fastboot.
You would have to get the necessary fastboot drivers working on your PC, extract the Asus firmware file twice and copy the file named "blob" to the folder where your fastboot.exe is.
Now, I would feel a whole lot better if somebody with more experience than I have - namely
@sbdags & Co - would confirm this, but I think the commands would be, from a command prompt opened in your fastboot.exe directory
Code:
fastboot erase system
fastboot erase recovery
fastboot erase boot
fastboot erase userdata
fastboot flash system blob
fastboot reboot
But please - don't take my word for it....