I have also posted this in Croatia but thought I might get additional insights here.
We fly into Zagreb and currently are flexible on time/days.
I was thinking:
--Arrive Zagreb/overnight to recup
--Get car, drive to Ljubljana 2 nights
--To Lake Bled few hours; start Julian Alps loop. Overnight Bovec
--To Rovinj via Piran; overnight Rovinj
--Enjoy Rovinj AM; to Plitvice Park PM. Overnight Plitvice
--Park early; to Split in PM
I know it's a lot to pack in with multiple hotels, but we are fairly accustomed to that.
If you had 6-8 nights, how would you mix and match this better?