The problem was in my network - specifically our password policy required 15 character passwords while the install script had an 8 character password hardcoded. The solution was to :
*edit the install script to use a password that passed muster with the network requirments,
*manually install SQL Express 2012 using the manual process in the docs
*use SQL Management Studio to the disable the password enforcement on the "sa" account
*edit the install script back to the original password Zetadocs wanted
*run setup.exe again to install the Archive Service