There are ways of doing this using Terminal but I tend to stay away because it’s outside my comfort zone. However if you are a Terminal pro, then I refer you to the video below titled “How to Make Bootable USB from ISO/IMG file in | Mac OS | Linux | Windows | 2016”.
There is also a great article about it on osxdaily.com.
For me.. I happen to have Parallels Desktop (warning: this will cost you $) on my Mac and run a copy of Windows 7. So it’s from that environment that I can run a free portable app called “Rufus Portable” (provided by PortableApps.com) which allowed me to create a bootable USB from an ISO image. There might be something in the App store for Mac that can do this but at the time I did not come across anything that could do the task other than doing the deed in Terminal.