If you have different versions of ZBrush 4 and above installed they can be used together with GoZ as the main components remain the same, but it’s not possible to work on the same project between multiple versions of ZBrush at the same time. Once a file has been created or saved in a newer version of ZBrush, it may not be opened by any earlier version.
For example, if you have a file that you’d been working on with ZBrush 4R3 and then save it using ZBrush 4R4, it will no longer be possible to open it in version 4R3.
GoZ cannot get around this restriction. It can be used to open files from earlier versions of ZBrush but it cannot be used to send files to an earlier version. The only way to get a file into an earlier version of ZBrush than it was last saved in is through the OBJ format.