There is no "Zionist holiday" but there is Purim which arrives in a few days. As that event happened thousands of years ago and has no modern parallel, that in itself is no cause for Iranians to hate Jews or Israelis and most don't: many Jews still live in Iran and Iran-Israel relations were quite good under the Shah.
However, I can see how Purim makes the mullahs and their followers scared and worried. Purim is a commemoration of an occasion where gangs of Jew-haters (not just Persians but other nationalities throughout the Empire) publicly plotted genocide against the Jews to be carried out on a specific day but the Jews armed themselves and killed the Jew-haters before the gangs could carry out their deeds.
The mullahs seek to dominate the middle east and destroy Israel but Purim strongly suggests that the Jews, while they will put up with verbal abuse and won't engage in empire-building, nonetheless won't allow the mullahs to fulfill their dreams of tyrannical domination and genocide. And for that us Zionists are hated by them.
No, The Jewish guys did not arm themselves. The Jewish Princess of Persia found out about the plot and told the king that the gang is going to perish her family. The Persian king (Xerxes) armed the Jews and let the Jews kill them all.
The Queen of Persia was named Esther. There is a book named after her in old testament.
The king who saved the Jewish folk is Xerxes. You probably know him because of movie "300"