hi, from airport to sunyatsun ,,,,,hall, t takes about 35 minut by taxi, from memory hall to railwaystation it takes 10 minuts by taxi, then waiting inline for ticket to shenzhen buyig tickets then wait for your train and abording train may take more then 30 inuts, train from guangzhou to shenzhen takes 70 minuts, then from louhu to louwu it takes 5 minut, then chacking in and taking subway to airport changinging MRT lines all may take one hour, see yourself please if it is enouphe time to go.

Guangzhou city to Airport takes about 30-45 minutes. Guangzhou city to HKIA takes a minimum 3 hours. You are cutting it close as it is, I don't think you will make it even if go direct from Baiyun Airport to HKIA.

To clarify, 3 hours by bus. About 2 hours if you take the train from East Railway Station to Hung Hom in Kowloon, HK.