After I posted I looked at it a bit more and saw that google could get me to Budva in Montenegro in just under 2 days. And I once cycled from Budva to Shkoder in a day.
That included a Flixbus leg from Zagreb down to Dubrovnik. Flixbus have bike racks so that bit might work (for maybe four people per bus - how many entries are they expecting?), but it also included a Globtour Croatia bus. I checked their bike carriage policy the other day, and it says they take bagged/boxed bikes in winter but not in summer as they are too busy! If you pack your bike small and ask nicely, you might get on, but no guarantee.
After I posted I looked at it a bit more and saw that google could get me to Budva in Montenegro in just under 2 days. And I once cycled from Budva to Shkoder in a day.
That included a Flixbus leg from Zagreb down to Dubrovnik. Flixbus have bike racks so that bit might work (for maybe four people per bus - how many entries are they expecting?), but it also included a Globtour Croatia bus. I checked their bike carriage policy the other day, and it says they take bagged/boxed bikes in winter but not in summer as they are too busy! If you pack your bike small and ask nicely, you might get on, but no guarantee.