Idk how to build her but a friend told me to go ap so this is how I currently build her. Dorans Ring+Hp Pot Boots>Merc Treads Fiends Codex>Deathfire Grasp Sheen> Trinity Force Starks Fevor Bloodthrister
Usually the game doesn't last enough for me to get Bloodthrister. Anything need changing?
boots + sheen first codex second soul stealer (some might say not to but honestly I have never seen a decent poppy feed even on a terrible team that is feeding they still rarely die and get decent kills/assists so it should be easy to sustain over 10 stacks) codex to deathfire sheen to lichbane zhoynas
and you should be able to combo just about anyone down to 1/4 hp instantly at that point (since a lot of these things work of % of hp as well as flat damage) if not kill them outright with one combo.
- Merc Treads or Sorc Shoes (depending if you want survival or more damage) - Sheen - Deathfire Grasp - Sheen > Lich Bane
From there it's situational. Abyssal Scepter, Zhonya's and Void Staff are all good items. You can also choose to build more survival, but your main job is to really use your ultimate on a prime target, take them out and run the hell away.
Team Fortress 2: Static: http://www.youtube.com/watch?v=a4XjtYxfqjs