Very easy to get this super fast if you don't want to read the essay below here is a video
Load up the tutorial world. You need to make a Splash Potion Of Weakness and a Golden Apple (Golden Apple has to be made with gold bars NOT gold blocks!).
Splash Potion of Weakness - To make this you need a Vial of water (Potion brewing tutorial area),a Fermented Spider Eye (Sugar, Spider eye & Brown Mushroom) and Gun Powder (fireworks tutorial area). Add these together to make the potion.
Golden Apple - To make this you need Gold Bars (In the floor of the church at Co ordinates X: -115, Y: 69, Z: -80) and an Apple (In a chest at co ordinates X: 0, Y: 32, Z: -5)
Once you have both of these head to a village then save once night begins. exit and reload but this time on hard and I advise you turn off auto save. Let the zombies turn one of the villagers then trap the infected villager so they can't get away or hurt you.
Throw the potion at them using
Then Cure them with the Golden Apple by pressing