SharePoint 2010 : Delete extended web application of any zone

You cannot see extended web application in the CA. you have to select default zone web application.

 you can delete extranet/intranet/internet extended web sites using below steps

Central Administration > Manage Web Applications > Select your  Web Application as shown in picture > select Delete from ribbon > Remove sharepoint from IIS website

Select IIS web site and zone to remove

Using Powershell

Remove-SPWebApplication -identity http://sitename -Zone {Default | Intranet | Internet | Internet | Custom | Extranet} -Confirm

his command removes the zone that you have specified for the Web application extension at http://sitename. This command does not remove the content databases or the IIS Web site.

 Note:

Be aware that this cmdlet can be used to delete the Web application, so be sure to use the appropriate parameters.