Do i need to apply for a visa or is a Guangdong 144 hour visa enough?

Hi,
i'm traveling to Seoul next month from Amsterdam. Now when I go to Seoul I fly the following route: Amsterdam - Guangzhou - Seoul. I know that a 72-hour or a 144-hour visa counts for this flight. Now my route back to Amsterdam is the following: Seoul - GZ - Beijing - Amsterdam. For this flight I can't find any information about a visa between these two cities. So do I need to apply for a normal visa or is a 72-hour or 144-hour visa enough? Can someone help me with that?
Thank you in advance.