From what I understand, if zirconium is in powder form, it can easily ignite. The trick is, that it has to be in the air. If it is in powder form yet is on a pile on the ground it may be more difficult to ignite. One thing it holds over magnisium though, is that burning magnisium doesn't like water, it really doesn't like water. Zirconium powder has a lower combustion temperature then magnesium so the reaction shouldn't be as bad. If you want to see how it reacts with fire,
magnesium fire