In 1941 Hitler gave additional areas to Italy after the German conquest of Yugoslavia, which Italy gave up after it switched sides in 1943. Tito tried to grab Trieste in 1945 but was forced to remove his troops after 40 days. Zadar, Istria, Rijeka, and the Adriatic islands went to Yugoslavia.
Istria still has an Italian-speaking minority but I don't know about Zadar.
That 40-day occupation of Trieste by the Yugoslavs was brutal. Thousands were killed and many others disappeared into Tito’s gulags.