That's against the Warzone rules matey:
https://www.warzone.com/wiki/Rules3.You shall not operate more than one Warzone account in a way that gives you an advantage in a game, tournament or ladder.
Playing 2 accounts in a 1v1 tournament would give an advantage in the way that the person would have 2 chances to win the tournament whereas other players would only have one. Also it would mean that the alt and the main would be matched up against each other in a game from the tournament which essentially means a person would play against themself.
Edited 5/4/2019 14:08:52