If your father-in-law doesn't have a copy of birth certificate, in this case, please provide me detailed information: his full name, his date and place of birth, and names of his parents.

He doesn't have to present in ZAGS personally, he can act through his authorized representative. If you have somebody in this region, I can prepare the power of attorney, but it will be physical power of attorney, not a digital. However, I am not sure that ZAGSes are working for public during pandemic of coronavirus. But you can take a risk and check. Otherwise, I can obtain Birth certificate for your father-in-law.