A sysop uses this command to accept an approved package permanently into the realm. This requires that the sysop repackage the project, causing it to be signed with the sysop key unless it was originally packaged by the sysop in the first place (which is the typical case on private or internal organizational realms).
The typical way this is done is to execute
zx review PackageID first, which unpacks the project in the local system for review, and then after reviewing it, running
zx package UnpackedLocation, and then finally
zx accept PackedZSP on the file created by the previous step (and then removing the review directory and .zsp if they are no longer needed).