You will spend about 30 mins by train from Kowloon to Shenzhen.
831 miles
1,184 km
607.02 kilometres (377.19 miles)
About 1400km or one whole night on train.
In China we count by how many hours by highway bus it is so easy to travel by high way bus. Every half hour there is a bus leaving in two cities. It normally take about 2 hours by bus