This route begins with Zagreb's continental rhythm, crosses to Zadar's compact peninsula, gives Split a full palace day, stays on Hvar after excursion boats leave and finishes inside Dubrovnik's southern transport logic. It is more varied than the seven-day route because the extra nights create two useful evenings rather than merely inserting more daytime attractions. Zadar's waterfront and Hvar Town both change character around sunset; sleeping there is the point.
Plitvice is the conditional choice. With a rental car and an early start, visit the lakes between Zagreb and Zadar, keeping luggage concealed and reserving the correct entrance and time. Without a car, joining a timed park walk, managing bags and reaching Zadar the same evening creates too many dependencies. Take the direct Zagreb-Zadar service instead and save Plitvice for the dedicated national-parks itinerary. This is a genuine trade-off, not a failure to complete a national checklist.
Return the car in Split before boarding for Hvar. Passenger services may arrive in Hvar Town, while the vehicle ferry uses Stari Grad on the opposite side of the island; those names are not interchangeable. The direct Hvar-Dubrovnik link is seasonal, so verify that hinge before buying non-refundable island and Dubrovnik rooms. If it does not run, shorten Hvar or return through Split by ferry and continue south by bus. The route rewards travellers who let transport set the skeleton and then choose fewer, better experiences within each base.