Can't extract the resourcepack file

Disable the protection option.

config.yml

  zip:
    protect-file-from-unzip:
      enabled: false
      extreme: false

This is the option to protect the zip file from unzip. Be careful when disabling it, everyone can unzip your file if you don't protect it.

Read compressed resourcepack

If you need to get the content of the resourcepack without extracting it, for example for debug purposes, you can use the /iazip --uncompressed --apply-to none. This command will create a new folder output_uncompressed in your ItemsAdder folder. Here you can access all the files and do your checks.