Eh, it's a pretty guarenteed conversion if they kill you, though how useful your biomass is depends on what state you are in at that point, I guess. If all else fails they seem to resort to making zombie-carpet. They're of the "Dead flesh nearby" kind of brand, essentially, rather than infecting the living as such. Though they do infect the living beforehand, and it does have consequences, it isn't fatal on it's own.

They are, however, one of the most durable types you're likely to encounter and quite dangerous too.

In this specific scenario? Numbers, if genuinely overwhelming, might work, as they can't replace their losses from the attacking zombies. However, they'd likely be able to render many zombies harmless for each of their own neutralised and have a much more balanced range of threats on their side, what with the different varieties.