About hongkong visa.

As an Indian passport holder I am having a Chinese tourist visa and I want to fly to Hongkong and then go to Shenzhen from HK airport.
My Q ?-Do I also require Hongkong visa to go via Hongkong to Shenzhen,also is my Chinese tourist visa eligible for entry to Shenzhen from Hongkong or I have to get another visa from Hongkong to go to Shenzhen?