欲言又止yù yán yòu zhǐto want to say sth but then hesitate
賠了夫人又折兵péi le fū rén yòu zhé bīnglit. having given away a bride, to lose one's army on top of it (idiom); fig. to suffer a double loss after trying to trick the enemy
玄之又玄xuán zhī yòu xuánmystery within a mystery; the mysteries of the Dao according to Laozi 老子[Lao3 zi3]