Hi ujjj0008,
I don't know if you use a PGP Viewer from Symantec Encryption Desktop than you can only drag and drop PGP Zip file. Although this is not fully automated option but amount of the steps is limited.
Also if you have got a SED installed so just by clicking on PGP ZIP (right button) you can choose Symantec Encryption Desktop > Decrypt and Verify option
Also just by one click on PGP ZIP file SED will open allowing you to edit encrypted file.
Apart from this we offer a PGP Command line which can meet your requirements but this is additional product for additional charge.
You can also have a look into this thread:
https://www-secure.symantec.com/connect/forums/automating-pgp-file-decryption
HTH