Create URL aliases for Entityform submissions
Note: This answer only applies specifically for the input form (I misunderstood the question above)

I was able to accomplish this by using simply modifying the entityform made configuration.


Go to /admin/structure/entityform_types
Click on the edit link for the entity form you wish to change
Scroll to the bottom and in the URL path settings set the specific custom paths that you wish
Save


It's that easy and it works for both the preview and the actual form :)