Germany passport holder to Zhuhai via HK

Heidi, you are perfectly allowed to do that, anyway this will not be a visa free transit, but you will apply for a Zhuhai visa on arrival when you arrive at Zhuhai port that is located on the artificial island just in front of Zhuhai. In other words, you will clear Hong Kong formalities and take a bus toward Zhuhai port. When you arrive there, you will approach 3 day Zhuhai VOA office (counter) where you will apply for this visa. The price is 168 CNY for a German citizen and it is advisable to pay for this visa in Chinese cash that you can easily obtain at one of many Hong Kong money changers. You will get a sticker in your passport and be allowed to proceed and after that to stay and explore Zhuhai area. After your stay in Zhuhai, you can freely return back using the same way to Hong Kong.

Once again, this is not 72 hour or any other kind of visa free transit, but a travel with relying on Zhuhai visa on arrival.