Croatia for a week....where to go?

Sounds like a lot of driving and not a lot of actually being anywhere. I have not been to Zagreb so can't say for sure, but my sense is it's not among the top highlights of CRoatia for most visitors. I'd skip that day and go straight to where you really want to go. You're wasting the better part of a day nearly everywhere - wasting most of a day driving from Zagreb to Rovinj. No time to actually see Rovinj or Pula, then you use up most of a day driving to Plitvice, sleep there and - no time to see Plitvice, you have to move on. Rinse, lather repeat. I think you need to cut your itinerary in half or nearly so. You would do better to skip 2 or all of Zagreb, Plitvice and Rovinj - because they're far from each other and from everything else - and focus on the southern coastal area (Dubrovnik, Split, Hvar, Korcula). If skipping all those would kill you, then drop Rovinj/Pula - it's just too far out of the way and you do not have enough time (and I say this as someone who travels at what most here would consider a frantic, unrealistic pace). You could do Zagreb, Plitvice then press south - at least that wouldn't involve a huge zigzag that would eat 3 days. It would still be a ratio of driving-to-being-somewhere that's weighted too heavily on time in the car, but at least it's physically possible. Yes, it is easy to drive around (except in the old city centers, where it's impossible), but most roads are small and the going is slower than you might expect. Hope that helps.