I have ZB 4.0, 4R2, and 4R4 installed. Why? I don’t know. Is there any good reason for keeping earlier versions? (A good reason for NOT keeping them is to free-up space.)
I usually keep mine for a few weeks just in case the newer version turns out to be pretty unstable (one of the v4 versions seemed to be) . If the newer version checks out during that time, then I get rid of the older one.
If you use GoZ you will most likely want to keep the earlier versions. This is because they use the same folders for sending data between apps via GoZ. So if you uninstall one of the earlier versions it will remove those folders and GoZ won’t work anymore. In that case you would need to reinstall 4R4 and reactivate it to restore GoZ functionality.
Of course, if you don’t use GoZ this isn’t an issue.