How did the zhou dynasty come to an end?

As with so many famous (or even infamous) political powers throughout human history, the Zhou Dynasty of pre-imperial China came to an end through a combination of two factors. First, internal struggles among powerful entities in the Dynasty weakened it to the point of vulnerability to outside invasion. Second, external forces in the shape of the Qin Empire were just at this point engaging in aggressive expansionism. The result of these factors was the toppling of the Zhou Dynasty in the 3rd Century BC/BCE and the founding of the legendary Imperial Period of China.