Flights to Zagreb, Croatia, check on the web sites of airline companies:

Airport Split – Split
The transportation options from Airport Split to Split you can check here:  

From Split to Brač, check the schedule of ferry lines on:

Transportation from ferry port in Supetar to Postira (Hotel Pastura)
We kindly ask participants to plan their ferry line according to the bus timetable on these pages:
Also, taxis are available in Supetar, so you can use them but at your own expense.