hi,
refrence from the article
http://blog.blksthl.com/2012/12/03/a-guide-to-alternate-access-mappings-basics-in-sharepoint-2013/
Left area Internal
URLs
Right area Public
URLs with a zone
Middle area Zones,
is what connects Internal URLs to Public URLs, many to one.
Internal URL redirects or transforms to a Public URL, from left, to right. The URL on the left, is what you
enter in the address field in your browser, the Public URL on the right is what you will see once there, this goes for visible and invisible links as well.
Internal URL format: Protocol + URL (+non default port)
Public URL is the address of the Web Application for one of the five zones available. The Default must be filled out and has some special properties/uses,
the other four are optional. You can only have five Public URLs per Web Application.
This is the URL that the browser will be redirected to in the end.
Public URL format: Protocol + URL (+non default port)
Zone is a label representing a Public URL, the zone is used to connect an Internal
URL to a Public URL. The zone names has no relation what so ever with the four Internet Explorer security zones (Internet,
Local Intranet, Trusted sites and Restricted sites) and could just as easily been named 1,2,3,4 and 5. A zone can also represent an authentication provider.
Zones: Default, Intranet, Internet, Custom, Extranet
so it clearly says that Internal url will not be shown in browser only public URL will be shown.
So in your case i suppose what you want to try is not possible.