South African needing a new Chinese work visa

My partner and I have been working in China for over a year, we recently finished working and our work visas have expired today on the 4th of September, however we are in Hong Kong and came here on the 31st August because we were offered a new job in Shenzhen. We want to know, is it possible for South African citizens tho were previously in possession of a z visa, to apply again here in Hong Kong to work in China? We would like to know if this is possible and which documentation would we need from our new employer to apply for a Chinese work visa.