Hi @Ian_Robson,
At this time this is not a possibility in Roon. Once a zone is grouped you will need to ungroup it to use it individually.
Since this behavior is currently working “as designed”, I’d like to recommend adding your voice to the Feature Request section of Community. Our product team and developers keep a close eye on that category, so that’s definitely the best place to propose a change like this and get feedback from the Community.
There is an existing feature request you can see here: Save Grouped Zones