Zusia is most likely a variant of
Zuzia (a diminutive of
Zuzanna), while Zosja is most likely a variant of
Zosia (a diminutive of
Zofia).
masculine list:
https://www.behindthename.com/pnl/191050/124079feminine list:
https://www.behindthename.com/pnl/191050/124080