What Is The Best Way To Compress A File

I have created an ISO Image with “XBOOT”, size is 5.6 GB. I don’t want to burn that ISO on 8.5 GB DVD. I want to compress that ISO file and wanna burn on a DVD with 4.7 GB of space. I have tried “Ultra ISO”, but it’s creating some weird image, not the Standard ISO. So is there any way to accomplish my mission? :)