The second quest of The Legend of Zelda is what you get by having completed the game once. It is more difficult than the first quest.
In this movie, the authors enter ZELDA as the player's name to start the 2nd quest without having to complete the game first.
This is a 666 frame improvement over the previous movie thanks to better optimization, be sure to read the author's submission notes for more information.
Watch this run being played back on a real console.