Final answer:
On Parshat Zachor, the mitzvah to remember the attack of the Amalekites on the Israelites is fulfilled by listening to the reading of a specific Torah portion in synagogue, usually on the Shabbat before Passover.
Step-by-step explanation:
The mitzvah performed on Parshat Zachor is the biblical commandment to remember the Amalekites' attack on the Israelites during their exodus from Egypt.
Observant Jews fulfill this mitzvah by listening to the specific section of the Torah that recounts this event, which is typically read in synagogues on the Shabbat before the Jewish holiday of Passover. This remembrance is considered so important that Jewish tradition treats it as a positive commandment incumbent upon every adult Jew.