At the moment it is not possible to mass update Zabbix Maps from the Zabbix Frontend. This posses an issue when a Zabbix setup has a lot of users that created maps on their own user. 

When we want to delete users this means we need to manually try to delete an users, the change the owner of the map. 

Of course, this is not viable in a big environment and a mass update map owner would fix this issue.