If any program can somehow convert .zdb files to .zdl files, it would be DesignPro label and business card making utility from which both of these files originate. Whenever this conversion is useful or even really possible could not be reliably verified. It may be possible that zdb is a format used in some older versions and it was replaced by zdl files in the latest versions.
Convert DesignPro label design to DesignPro label design.
We found 2 software records in the database related to .zdb to .zdl file format conversion.
Microsoft Windows software - convert zdb to zdl on Windows
A software for Avery label design and printing
Convert from zdb file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned zdb to zdl. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert zdb to zdl on OS X
Program for control all Avery products and create documents