Visa Requirements. Thank you

Hi, could you please advise if we are required to apply for a visa in our scenario with an Australian passport and also a Malaysian passport :

1. Travelling to Seoul via Guangzhou, China transit approx 15 hours transit.

2. Travelling back from Seoul to Dalian, China transit approx 9 hours
Travelling back from Dalian, China to Shenzhen transit approx 7 hours
Lastly, flying back to Australia from Shenzhen.