Well, this is an unusual format isn't it. Very "cutting-edge," so there isn't much support around as you might expect. But there is a way.
***I should mention that you can do this with UltraISO, but you have to buy it, or use a free trial which will run out eventually. I am a fond believer in freeware, so this is a tutorial for burning .isz that will cost you nothing. =) ***
To start you'll need to download and install:
Daemon Tools Lite: http://www.daemon-tools.cc/dtcc/download.php?mode=Download&id=81
ISORecorder: http://isorecorder.alexfeinman.com/
ImgBurn: http://www.imgburn.com/index.php?act=download
1st off, install Daemon tools. When you do this, it will as you to restart. When it restarts, it will complete the setup. ***Be careful however as there is one part towards the end of the install that if you click to accept, will sign you up to annoying adware that daemon uses to generate funds. Simply click decline and you will be spared its wrath***
2nd Install ISORecorder and ImgBurn ***You only need to install imgburn if you dont have a burning program already, that is capable of burning iso's
3rd. The latest version of daemontools has isz support.
So, rightclick on the lighting bolt on your taskbar (daemontools icon) then goto --> Virtual CD/DVD --> Device 0: (There should only be one) --> Mount Image. Navigate to your isz image file. This will mount you isz file as a virtual cd. It will appear as if you have inserted the cd.
4th. Find the virtual cd in my computer. Right click on it. ISORecorder should have added an option to "Create Image from CD" - click on it. Follow the cd recording wizard.
5th. You will now have an iso file, made from your original isz. You simply burn this with imgburn or just about any other cd burner.
Voila!