What's a full item build for Zed look like, anyway?
I don't think I've seen any LCS or Worlds game with Zed in it get past Last Whisper, BoTRK, Brutalizer (most of the time they don't even make it to Black Cleaver) and Boots.
What would their last items be - a GA and maybe a Bloodthirster?
Depends on the enemy team, as always. BoRK, LW and Black Cleaver are more or less given; usually you want a Mercurial Scimitar on top, and then something else (Randuin's, Maw of Malmortius, Bloodthirster, GA, etc.) depending on the game.