A zvd file extension is related to the Zyxel Voicefile (Z-Fax) audio format.
ZVD file extension - Zyxel Voicefile (Z-Fax)
What is zvd file? How to open zvd files?
File type specification:
The zvd file extension is associated with the Zyxel Z-Fax device.
Zyxel Voicefile is audio format used for transferring voice over the Z-Fax a fax and modem devices developed by ZyXEL Communications.
The Z-Fax seems to be obsolete product.
This zvd file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.