There are only two direct buses from Wuzhen to Shanghai South Bus Station. You can take the one at 6:40am. It arrive in Shanghai 2-3 hours later. Then you can take Pudong Airport shuttle bus line 7 from the South bus station to the airport.

Thank you Mr Jamie,
What about other routes (through Jiashan, Tongxiang or else)? My goal is to have as much time in Wuzhen the morning as possible, and then go to Pudong to arrive by 2 pm: it could include buses, taxi, trains, not necessarily direct bus.
Best,
Ilya

If so, you can go to Tongxiang first from Wuzhen. Many bus choices from Wuzhen to Tongxiang and from Tongxiang to Shanghai. There are bus every a few minutes. There is a bus from Tongxiang to Shanghai at 9:30am. You can take this one. It takes another 1-1.5 hours from Shanghai South Railway Station to the airport. So, give enough time on the way.