: In some PLC (Programmable Logic Controller) environments, "ILD" stands for Instruction List Diagram , a type of low-level programming language. The "XXF" could be a machine-specific identifier.
Providing a bit more context on where you saw this string will help me give you a more precise explanation. XXF.ild.aXX.zip
Since this specific string does not correspond to a widely known public dataset or standard file format, Breakdown of the Filename Structure : In some PLC (Programmable Logic Controller) environments,
: The "XX" markers are frequently used as wildcards or redaction marks in documentation to show users where their specific ID or variable should be placed. "ILD" stands for Instruction List Diagram