A good balanced visit to Syria is for a week. Your direction depends largely on what you would like to see in this specific period of time. To add the bluish green colored Euphrates is an extra flavor to the richness of the itinerary. Transfer to Palmyra. After breakfast, full day sightseeing of Palmyra, the temple of god Bel, the tombs, the national museum.
Lunch is in a local restaurant.
The castle of Ibn Maan is to be visited to see the sunset over-shadows Palmyra. Free morning to explore Palmyra. Drive to Deir-Ezzor for lunch. After breakfast, drive up stream then follow a side road to explore the city of Resafa,which possess a magnificent 5th century churches. Continue our drive to Aleppo.