Zero is a task manager of sorts for your Windows Phone that, in many ways, marches to a different drummer. It might be more appropriate to call Zero a gesture based "To Do" list manager than a task manager though.
There's really not too much to Zero but there is a learning curve unlike any other Windows Phone app that you may run across. Zero relies on screen gestures for navigation and while the gestures aren't difficult, if you forget to swipe right when you swipe left you could have problems.
Once you get the hang of Zero, it's a really nice Windows Phone app that helps you tackle your To-do lists.