Is it possible to have them both to switch back and forth? Or is it you can only have one or the other? Thanks for the help

You can install both Rise of the Reds and Shockwave together in the same game directory of Zero Hour. You can also switch mods as long as you start them via their respective launchers. Make sure you appropriately clicked "exit" on a launcher before you start launching other mod. Also, this does not work properly when there's unofficial patches or addon mods (from NLS) installed unless you remove them or rename their files extension for the time being.