You can modify services of the default zones but you cannot modify Security Type of the default zones. For some of the default zones, you can modify the name also.
Check boxes of the default zones in the Zones table are unavailable for selection.
For the complete list of the default zones, refer to Default Zones.
To edit a zone
Navigate to OBJECT | Match Objects > Zones.
Hover over the zone to be edited and click the Edit icon.