I am planning a trip to Slovenia and Croatia and I've heard that zip lining in Croatia is incredible and I am wondering if there are any recommendations of the best area to zip line.
I can only report that in 2015 I saw people ziplining in or very near Pazin, the administrative center of Istria.
I did this one a couple of years ago. Okay, not Croatia, but close, and in a stunningly beautiful country. https://meanderbug.com/listings/longest-zipline-across-tara-canyon-montenegro/