A PKG is encrypted. You cannot just unzip it.
Checkpoint: After extraction, look for EBOOT.BIN (the executable) in the USRDIR folder. If it's missing, extraction failed.
Create a bootable ISO (macOS installer): how to convert pkg to iso
hdiutil makehybrid -iso -joliet -o Installer.iso Expanded/
This method works for macOS High Sierra and older. For newer macOS versions, use createinstallmedia instead.
A direct, one-click "PKG to ISO" converter does not truly exist. This is because the two file types serve completely different purposes: A PKG is encrypted
Therefore, "converting" means extracting the PKG and then rebuilding the extracted files into a bootable disc structure (ISO). This is only possible for PS3 PKG files (and some PS2 Classics PKGs). PS4/PS5 PKGs cannot be converted to ISO because their security and file systems are incompatible with the optical disc standard.
The act of converting PKG to ISO treads in legally ambiguous waters. Under the U.S. Digital Millennium Copyright Act (DMCA), circumventing DRM (i.e., decrypting a PKG without authorization) is prohibited, even for personal backup. The required decryption keys are almost always derived from hacked consoles or leaked Sony code, making possession and distribution of conversion tools a potential legal liability. Checkpoint: After extraction, look for EBOOT
Furthermore, converting a legally purchased PKG for use in an emulator is defended by some under fair use for format shifting and archival, but this has not been conclusively tested in court. Distributing the resulting ISO (which removes PSN DRM) is clearly copyright infringement.