Yes, if you have a GDL object that computes something, it can be scheduled via the 'Additional Parameters' option.
No objects / elements are 'aware' of any others, though, so from within GDL you cannot compare one zone to another.
A custom add-on could be programmed to access stuff like that, though not an easy or user-oriented task.
From a user point of view, the ODBC add-on may be the way to go, at least for comparing zoned, etc. From Microsoft Access, you can perform whatever kind of joins and comparison calcs you want and display it attractively in a report ... that is then sent to a PDF that can be placed on a layout. But, with various manual steps ... and with careful naming of the zones to let your database queries identify the old vs new easily. All of this is still beyond the normal skill level of most architects.
Alternatively, schedules for each group of zones can be published to text csv files which can then be brought into Filemaker (Mac or Win) or Access (Win) to do the data join and comparision.
Bottom line - anything other than simple scheduling is way too complicated in ArchiCAD and the process should be made easier.
One of the forum moderators
AC 28 USA and earlier • macOS Sonoma 14.7.1, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB