You have a remote Hyper-V host with virtual machines running on it.  You enable Remote Desktop on the remote host and connect to the remote host from your workstation using Remote Desktop Connection.  Your change your RDC window to fullscreen mode. 

Now, via your RDP connection to the remote host, you start one of the virtual machines on the remote host and open the virtual machine in a Virtual Machine Connection window on the remote host.  You change the VMC window to fullscreen mode.

You now have a fullscreen view of VMC on top of a fullscreen view of the remote host via RDP.  How can you get back to the RDP session to the remote host?

Drag the VNC session toolbar from the top of the screen towards one side to expose the RDP session toolbar beneath it.

Mitch Tulloch is a eight-time recipient of the Microsoft Most Valuable Professional (MVP) award and widely recognized expert on Windows administration, deployment and virtualization. For more tips by Mitch you can follow him on Twitter or friend him on Facebook.