Do you really only get Hexdrinker and its upgrade if you're not doing well? The extra MR and its passive is really useful even when not doing well. Moreover, opting for Black Cleaver even when doing well really weakens your ability to snowball, as it translates you from an assassin to more of a bruiser. When doing well, it's much better to take Duskblade of Draktharr rather than taking it late game. The order for duskblade and cleaver therefore, are backwards. Another thing I find questionable is opting for Mercurial Scimitar when doing poorly. This item is not taken for the magic resistance, but for its passive to cleanse status effects.

Do you plan to add explanations to make this build a guide? I understand it's not a full fledged guide yet, but your build order seems to be very restrictive when Zed actually has some flexibility.