I intend to go to Zhang Jia Jie from Guangzhou in late June. Please advice me on how to get there .

You can travel by direct train or air.
When you arrive at ZJJ Railway Station, you can walk to the nearby Central Station to take a direct bus to reach the scenic area. The train duration is about 14 hours and a little longer.
By air, upon your arrival, you can take the airport shuttle bus to the local central bus station to take a direct bus to reach the scenic area. The flight journey takes about 1.5h.