I have driven between them though not in one day. Honestly, I'd go with Google Maps. It may not be 100% accurate, but it's close enough. As you can see on Google Maps, there is an express highway that's inland a little so not much scenery but very fast. If you really mean you are going to do this as a single day trip in one day(??), I don't think you really have any other realistic option except the fast highway. If you are doing this over multiple days, then just take your pick.
Sibenik itself is easy to get to from the highway. Zadar seemed to take a while to get to once you got off the highway, FYI. Parking in Zadar can be a challenge - in Sibenik it's pretty easy.