I'm new to Ziva myself but I think you need to mirror your muscle meshes yourself (works like any other Maya geo ie duplicate, group, -1 scale, freeze transforms)
And to mirror your ziva setup you can use copy/paste with name substitution, described here
https://docs.zivadynamics.com/vfx/transfer.html?highlight=mirror
As said, haven't used this myself yet just skimmed through the docs.