How is it that the Marcheshes and Or Same'ach, Hilchos Megilah 1:1, give the explanation that women are not michuyav in the mitzah of Mechiyas Amalek and yet be michuyav in hearing Parshas Zachor?
Most Poskim indeed exempt women from reading Parshas Zachor as well. It is the Chinuch who says that they are Chayav, and the Poskim all challenge his view. (See the commentators on the Chinuch who attempt to defend his approach.)
Mordecai