Fast train or bus from zhengzhou to yangzhou.

For train, no fast train runs between these two places. The normal speed train spends a long time. So you are suggested to take bullet train to get to Zhenjiang South Railway Station first. It takes around 6 hours on the way. Then take a taxi to Zhenjiang Bus Station and take direct coach to Yangzhou in 30-40min.

For long-distance bus, you can take it from Central Bus Station. But it only has one schedule at 19:20. The ticket fare is CNY 240 per person. It takes around 11 hours on the way.
You can choose the way you like.