When an opponent is about to lose the game due to lethal infect and/or commander damage, before damage is dealt, activate Zedruu by paying ({R} magic symbol) ({W} magic symbol) ({U} magic symbol) , giving the opponent about to lose the game control of Lich's Mirror.
When the opponent would lose the game, Lich's Mirror causes them to shuffle their hand, graveyard, and all permanents they own into their library, draw seven cards, and set their lifetotal to twenty.
Because they don't own Lich's Mirror, they retain control of it, and because infect/commander damage is not reset, they will then attempt to lose the game as a state-based action.
This creates a mandatory infinite loop, which ends the game in a draw.