Are the prescribed post-prayer remembrances shortened for a traveler, or are the remembrances performed for each prayer?

For the remembrance (dhikr), one single remembrance suffices for two prayers if they are combined, because they are considered as one prayer. The greater of the remembrances mentioned for each prayer is taken, thereby encompassing the lesser. There is no harm in performing a separate remembrance for each prayer, but the first (method) is sufficient.