Time is not enough. Tongli has only a few buses back to Shanghai and the last one is around at 15:00. For the details of that day, you should ask the Tongli bus station. If you miss the bus, you can get back to Suzhou first, then to Shanghai.

thanks for all the answers. it is better to visit tongli or zhuzhouang?

In fact, these two places are all well exploited which means a bit commercial, because they are famous. This is understandable and will not hold you back from your exploration. Zhouzhuang is more weel known, entrance fee is more expensive than Tongli. Tongli is simpler in layout, with less rivers, bridges. So, I think you should go to Zhouzhuang. Enjoy!