We absolutely love Zadar. Not sure what your port times are but sunset is glorious.
Alfred Hitchcock once said : ” Zadar has the most beautiful sunset in the world, more beautiful than the one in Key West in Florida, applauded at every evening. ”
We really enjoyed the Archeology Museum and the Roman ruins outside. A very easy town to walk about.
Lunch recommendation would be Konoba Dalmacija - Tavern. We love calamari and octopus. Everything is melt-in-your-mouth. If there is a side of mangold (chard and potatoes with garlic), definitely have some. We ate at a number of lovely smaller restaurants when we stayed there a couple of years ago. Look at the menus and pick one.
Enjoy your trip.