Amsterdam - Xiamen - (<24hrs) HongKong - Xiamen - Amsterdam

Maxim, actually, if your transits in Xiamen are less than 24 hours respectively, you can enjoy the 24 hour direct transit. In this case, no entry permit is needed. Or if you travel by flight all the way and your transits in Xiamen are less than 72 hour respectively, you can enjoy the 72 hour free transit and no entry permit is needed either.
If you don’t have HK residence permit, it’s not easy for you to get entry permit for mainland PRC from HK.