It is of course fast but expensive to fly to Jiuzhaogou and fly back to Chengdu, since it only takes about 45 minutes for a signle way. However, you can also enjoy the scenery along the way if taking a bus from Chengdu, even if it will take about 10-11 hours.
So, I think you can take a bus to reach from chengdu, and then fly back to Chengdu, but you have to stay one night in or near the valley. The air tickets can be book through https://www.travelchinaguide.com/china-flights/chengdu.htm in advance.
It is about 152km between the two places.
Hotels in Jiuzhaogou are Sheraton Jiuzhaigou Resort, InterContinental Resort Jiuzhai Paradise, and New Jiuzhai Hotel.