since I'll go in Ljubljana and Zagreb, I would like to know how trains between these two countries are: are there frequent delays? Or maybe trains deleted? It's so important to me because I have to book the flixbus from Ljubljana to Italy, depending on train hour/delay. Thank you!
I cannot answer your question but want to point out that there is also bus service between Ljubljana and Zagreb that's not much slower than the train.
Ljubljana is a beautiful and very engaging city (as is Zagreb); I'd plan at least one or two nights in Ljubljana.
In 2019 we used Flixbus between Italy and Slovenia and then again between Slovenia and Croatia. Found it very easy to use.
In 2019 we took the train from Zagreb to Ljubljana. The train was on time. It's about a 2.5 hour ride. Very inexpensive. If you buy tickets the day before, the rate is about $9.00 one-way. I don't think you can buy them online. We bought our tickets at the train station the day before.