The zimage file is contained in the .tar, but still you need to flash the .tar file...
.Tar files seem like zip files and can be extracted, so to solve the windows showing the file as zipped do as O-T said:
Then start ODIN with administrator privileges and use the .tar file (ONLY TAR FILES) as PHONE, do not choose any other file and certainly dont tick re-partition, after all are ready (and your phone is in download mode and recognized by ODIN) press start.
If you failed and see the screen with "Phone/YellowTriangle/Computer" do not worry, just pull out the phone battery, leave it with battery off for 30 secs, put the battery back in, get your phone to download mode (guess you are putting your phone to download mode before flashing, right?) and try again using the instructions that you have read in all those posts!
After i read ur post i flashed again and it works again with root!
So final question. if i want to unroot do i just flash stock kernel and i am unrooted?