Ljubljana to Bled before Zagreb

First off, if you are thinking of going straight from the airport to Bled, there are buses
that run direct. Not sure there even is a train, and even if there is, it stops at the Bled
Jezero station, which is not all that close to the town area, especially with luggage.

Bled is fairly small, but you don't say anything about what you want to do either there,
or in Ljubljana. Without a car, or plans to use the local buses, a couple of days in Bled
would seem like enough, but the first day after your flight should probably be assumed
to be a wash. So 3 nights all together. But if you want to explore the area, and hike,
that is a whole different set of circumstances.

I would say 3 or 4 nights in Ljubljana as well if you are just planning on sightseeing.

Is there good hiking in Bled? or is there better hiking near by?

Lake Bohinj, a turquoise alpine lake inside Triglav National Park, has hiking trails and far fewer tourists than Lake Bled. From Ljubljana, Lake Bohinj is only 30 minutes beyond Lake Bled by bus.