What's the difference between Shanghai social security and Zhejiang social security?

In principle, there is no difference between policies and regulations. The difference is that the payment base in Shanghai is definitely higher than that in Zhejiang, so the payment amount will be higher. Similarly, the pension benefits in Shanghai are higher than those in Zhejiang.

Further reading: How to buy insurance, which is good, and teach you how to avoid these "pits" of insurance.