Jiuzhaigou and Huanglong are in the north side of Chengdu while Emeishan and Leshan are in the south side. You can go to the places in the north and then back to Changdu, then you can go to the places in the south. BTW, the road condition is not very good in some part of Sichuan Province, better keep noticing the news in that area since sometimes travelers can only get to Jiuzhaigou and Huanglong by air.