Was Al-Shawkani a follower of the Yazidi sect? What is the difference between Yazidism and Zaydism? And do both sects contradict the Sunnis?

Al-Shawkani was not a Yazidi; rather, he was a Zaydi. Due to the breadth of his knowledge, he began to follow what seemed most preponderant to him. The difference between Zaydism and Yazidism, and their disagreement with the Sunnis, can be found in Fatwas no. 47566 and 33552.