Croatia has one working holiday agreement, which is with New Zealand. The agreement was signed in 2014 and allows 100 participants from each country.
Guides
The Croatian working holiday scheme for New Zealanders
About
New Zealanders between the ages of 18-35 years are eligible to apply for 43 long stay visas under the working holiday schemes New Zealand has agreed with other countries.
40workingholidays.com has guides on how to apply for the visas, and how to get setup once you arrive.