i have a Zekrom with 415 attack, but i heard someone has a Zekrom with 752 attack. is that possible without cheating?
No, on the Zekrom page ( http://pokemondb.net/pokedex/zekrom ), the highest Atk stat possible is 438.
So that person with a 752 atk stat was either lying or cheated (his game). HTH!