As many of you know I have more that 1 version of Zorin loaded on my desktop ...... my question is ..... when I have an update appear will it include updates for say Zorin 16.3 and Zorin Pro Lite as well as the desktops being used with these OS's ...... Cinnamon ..... Xfce and Gnome ......
I believe that that the OS's do have different apts installed ....
Will I need to do an update for each of my Zorin OS's ??????????? .....
Since you installed everything from the existing repositories, you can rely on your regular upgrades to keep everything up to date. No extra effort needed.
Both OSs use the same kernel and firmware for your pc. Both also use the same graphics library. The only difference is what sits on top of all that to give you the lock screen, desktop and graphical manipulations (windows, icons, app menu, taskbar). They are identical in purpose but different in how each developer got there.
Why is this important? The kernel and libraries will not need separate updates. As Aravisian said, since you included the repositories and installed from apt, apt will take care of it.
You may get gnome updates while in cinnamon, xfce updates in gnome and Cinnamon updates in xfce, it all depends on what desktop you are using when you update. It doesn't change that all of them will receive the updates that are available for them.
If you were using KDE, it wouldn't be much different, as you don't have to be in a desktop environment to update a desktop environment (that's a Windows thing)!