Who is Hasach?
Torah Temimah citing Megilah 15a: He is Daniel. He is called Hasach because Chatchuhu (they cut him) from his greatness (which he had under the previous kings). Some say (like the Targum), he is called Hasach because all royal matters are Nichtachin (executed) through him.
Malbim: He was one of Sarisei ha'Melech. The king put him in front of her to be her confidant.
What did she command him about Mordechai?
Vilna Gaon: He should speak with him. Perhaps he will get him to say what is this [matter].
Malbim: She was unsure if Mordechai will trust him to reveal his hidden matters, so she commanded him to investigate [the reason for Mordechai's actions].
Why does it say "Mah Zeh v'Al Mah Zeh"?
Vilna Gaon: One who wants to know something clearly, he must know (a) what it is, and (b) why it was done.
Malbim: This is like an expert doctor - he investigates what is the illness, and the reason that brought it, i.e. the evil that is the cause. One can remove the effect only via removing the cause. Also Mahara Ashkenazi explained so.
