Primero, creo que debería ser:
Código PHP:
Ver original$default_conf = new Zend_Config_Ini(
APPLICATION_PATH . '/configs/application.ini',
APPLICATION_ENV);
Zend_Registry::set('default_conf', $default_conf);
$config_admin = new Zend_Config_Ini(
APPLICATION_PATH . '/modules/admin/configs/config.ini',
APPLICATION_ENV);
$default_conf = Zend_Registry::get('default_conf');
$config_admin->merge($default_conf);
segundo, que error te muestra ?