The Z fighting happens when two different particle systems emit too close to one another, the engine sorts systems based on distance, and if for example, a piece of debris from an explosion in the back flies past an explosion in the front, the engine will start having trouble deciding which system should draw on top of the other.
As far as I can tell, the sorting between individual systems isn’t something I can control.
Ah, I got the impression that the fighting occured inside one system. the one starting at 0:10 on the right for example. I don’t see that much overlap with another system, but some heavy flipping…
Argh, Gabe should give you magically cheap per particle sorting!! 
So are you using Houdini to create texture sheets to tackle this? I’ve been trying to go for a more gritty grenade/general explosion for my project
Would be keen to see what the main texture sheets look like? are you using houdini? Really looking and feeling good