At the longest I had the game sitting for about fifty minutes till it switched to night.
Breakdown has a random chance of starting at night when you start a new game, otherwise just play around or idle till the time changes. In order to have kills count you need to have the in-game time setting be night time. If a zombie gets alerted before you can sneak up on it, you can either use a sweep kick ability if your character has it and then just align yourself behind them or you can just keep mashing the kick button till they fall over or down to one knee and then align yourself. Get to one of those wide farm fields, tons of zombies and very little place to have one sneak up on you. You can also get silent kills entering crouch mode by holding for two seconds, then sneak up behind a zombie, hold and press once you're close enough. running at you) then kills on it won't count towards this. Silenced suppressor weapons are incredibly helpful but aren't mandatory. (If you don't already have him, don't bother unlocking him just for this Challenge unless you plan to unlock the Challenge while going for his achievement.) The The Ninja achievement in State of Decay: Year-One worth 39 points Execute 50 Stealth Kills at Breakdown Level 5 or Higher.
