The main difference between Zhoushan flying crab and Donggang flying crab lies in appearance and origin.

1. Appearance: The shell of Zhoushan flying crab is light-colored and slightly red, while the shell of Donggang flying crab is dark blue. In addition, the size of Zhoushan flying crabs is generally smaller than that of Donggang flying crabs.

2. Origin: Zhoushan flying crabs are mainly produced in Zhoushan City, Zhejiang Province, while Donggang flying crabs are mainly produced in Donggang City, Liaoning Province.

In general, there are certain differences in appearance and origin between Zhoushan flying crabs and Donggang flying crabs, but the specific differences may vary due to individual differences and environmental factors, and require specific observation and analysis.