I might like the car and driver OR BUS to go from Zhangye to Jiuzhaigou is this possible?

I'm afraid it is hard to achieve this by renting a car and a driver, because there is around 1,200km between the two places, too far. Then you may consider taking a train from Zhangye to Lanzhou and then at Lanzhou Passenger Transport Center, there is a bus to Jiuzhaigou at 07:00.

Thanks so much, about 24 hours?

Do you refer to the duration for the whole trip? No, it takes less than 24h. Trains from Zhangye to Lanzhou takes around 6 hours and the long-distance bus to Jiuzhaigou takes 10 hour or a little longer.