What kind of transportation do you take?

which is the cheaper way by train or by air,checking for prices and schedule of both

There isn't direct train from Zhuhai to chengdu, I think you can oonly take a flight if you won't like to make any transfer in between. The tickets price is changing from time to tome, you can get the real-time flight schedule and ticket price from China Flights(https://www.travelchinaguide.com/china-flights/).