You can reach Zaostrog:

By car 
-  By motorway from taking the Šestanovac exit
Then by state road to Zaostrog – 60 km
Journey time from Šestanovac to Zaostrog – 1h10min

OR-

by state road from Split to Zaostrog – 94km
Journey time from Split to Zaostrog – 1h 50 min
www.hak.hr

By bus
Total Journey time – 2h
Bus station Split
www.ak-split.hr

By plane 
Split Airport – distance to Split – 25 km
www.split-airport.hr
From Split to Zaostrog by car or by bus.