Using zone reordering , you can adjust the position of zones (z-index). This will be useful ,when you have overlapping zones in the layout you are using and if you want to bring one zone on top of another zone.
Please follow below steps to reorder zones :
1. Click on the Composition menu from left hand side and click on the + Add Composition button.
2. From the layout listing page -> Click on Edit against the layout
3. It will take you to the edit page. Here you can drag and position the zones from right hand side,where zones are listed along with their size and coordinates . Once you are done, click on Update Template and the zones are reordered.