this build may be considered stupid by someone who's used to play with the classic AD Ezreal build, but i play with this all the time and i think it's the best you can find.
AP Ezreal can deal very massive damage to enemys, making you able to take some triple, quadra or even pentakills in the teamfights.
i suggest to try it, and if you find it useful, please rate my build or leave some comments.
gl & hf
bye