Zajc's opera holds a special place among Croatian operas thanks to its indisputable musical merits and powerful patriotic charge. "There are operas, and there is Zrinjski," Boris Papandopulo once remarked.

Based on a historical event of the 16th century, when the heroic deaths of Nikola Šubić Zrinski and his garrison thwarted Ottoman plans for a campaign against Vienna, the opera has outgrown the bounds of a mere operatic title. Its musical and dramaturgical qualities are beyond dispute, and the work met with extraordinary success at its very premiere. Particular enthusiasm was aroused by the stirring oath of the heroes of Siget and the famous chorus U boj! (To Battle!).

Zajc's compositional hand is recognisable in its differentiated portrayal of two opposing worlds; alongside the historical figures of Zrinski and Sultan Suleiman, he also shaped powerful female characters – Eva and Jelena.