I'm looking to add a few blocks of text that would only display for the master user. I see there is a class for isMasterUser( $user ). Would that be the best one to use?

On standard theme context use something like this:

  if(zp_loggedin(ADMIN_RIGHTS) && $_zp_current_admin_obj->master) {  … } 

Within a function $_zp_current_admin_obj must be declared global if not already

Perfect. Thank you!