User blog comment:TheNewBuildGuy/Possibilities-- Jungle Zyra/@comment-5266525-20130227111309/@comment-199.84.62.94-20130227175728

I dont know about the other ones, but getting Mpen helps her clear times since it pushes jungle monsters' MR into the negatives, amplifying damage by the same percentage an equal amount of positive MR would decrease.

At least, that's what I remember.