Two Red Hat in the same computer

Hello,

I'm working on a testing department. I want to have two operation systems on the same computer.

In one case I want to have two Red Hat Enterprise 7 on the same machine and the other a RHEL6 and RHEL7.

Today, machines with UEFI think I can only have one operating system on a computer.
How I can have two operating systems on the same computer?

Thank you very much
Regards
Valentín