Ideally, i'd do this .....
- Zagreb 2 nights, it's not a brilliant city TBH.
- Drive to Plitvice via a town called Turanj and stop there to see the war memorial, not big but you literally drive right past it and stop at the pub for a feed. Spend a night locally near Plitvice or near the ferry ports around Jablanac.
- Grab a ferry to Island Rab, spend a few days exploring, it's a slower paced island but still great outdoor bars etc. 3 nights
- Drive to Split - 2 nights
- Drive to Makarska, great mix of beach and mountains, 2 nights, maybe 3 if warm enough.
- Drive down to to Dubronik, 2 nights.
Fly back from Dubrovnik to zagreb and look to take day trips from Zagreb to surrounding cities as the weather cools to fill out your itinerary.
If you see a sign that says Odojac, stop in, it's roasted pig on a spit. Just stop in, down question how shitty the place looks on the outside.
Here is my gallery when I was child free ...
https://alfiimages.zenfolio.com/f911526456