Thanks for posting.
The key for the line number change is whether you want to “import” the referenced IFC file into the gh document IFC file (that the plugin manages for you), or if you want to reference that data.
There is an append data option on the file import component, if you set that to false, the data won’t have records offset for any existing objects in the plugin database already set.
I’m actually working on changing this, in part it will be easier to have multiple ifc databases on the one canvas (but I might have to add some error checking to prevent unintended cross referencing).
There’s also some improvements relating to zones, I will reply to your email to access this new work in a plugin update. I’ve attached a modified version of your script that might help.
prove ifczones.gh (14.0 KB)