I have Zanji equipped with the spirit of the six samurai. I also have an Irou on the field. My opponent uses brain control to take my Zanji and attack my Irou. Who gets to draw the card becuz of the spirit? me or my opponent?

Neither player. Zanji is equipped with SotSS, and he attacks "your" monster, not your opponents monster.

Since you control SotSS, it is your effect, but your opponent controlled the monster, so neither player benefits.