To act in concert, with internal support coordinating with external action; to provide inside assistance in response to an external move.
为了成功举办这次活动，志愿者们在外场布置，工作人员在后台准备，大家外合里应，确保了活动顺利进行。
To successfully host this event, volunteers set up the outdoor area while staff prepared backstage; everyone coordinated from within and without, ensuring the smooth progress of the event.
Next Idiom