need help to write routes

hi, i am using ci3 with wiredsign's hmvc.

i have the users modules with two controllers 1) public_user 2)admin_user

these are the  URLs

http://www.mysite.dev/users/admin_user/showall

http://www.mysite.dev/users/admin_user/show/12

http://www.mysite.dev/users/admin_user/delete/4

http://www.mysite.dev/users/admin_user/edit/7


http://www.mysite.dev/users/admin_user/create


i want to replace users/admin_user with admin/user so that URLs become

http://www.mysite.dev/admin/user/showall

http://www.mysite.dev/admin/user/show/12

http://www.mysite.dev/admin/user/delete/4

http://www.mysite.dev/admin/user/edit/7

http://www.mysite.dev/admin/user/create

is there any way to achieve this without writing routes for each URL individually ?