Hi @chr1zz
If the quests are still Green/Yellow, then I’d click “not now” when the guide suggest pops up. If you already accepted, then just right click your current quest to open the guide window and pick the previous zone. If you already picked up a few quests in the new zone, then you may have to abandon them if the quest log gets full.
Currently I only use the “not now” option because I don’t do Dungeons atm.
You can always switch between zone guides. It’ll remember your progress.