IANAL - you instinct is good generally but you missed a key point.

Zuru is suing in CA to compel glassdoor to produce information.

Zuru is not suing glassdoor for breaking NZ law in CA. That would make this case go away very quickly.

Instead, Zuru is saying they intend to sue NZ individuals in NZ, but in order to sue, they need info from US based glassdoor.

there may be some kind of cross border agreement to facilitate information between NZ and US. Politics aside, i dont know if a US company could be compelled by a US court to produce information to sue chinese or russian citizens, under those respective laws/jurisdictions?