هل كانت عصا موسى -عليه السلام- "ثعبانًا" أم "حية" عند تحولها؟

There is no contradiction between the two verses, for the term "hayyah" (الحية) can refer to both the male and female serpent. As for "thu'ban" (الثعبان), it refers to the male, or it is said to be the large one among serpents, whether male or female. Some scholars have mentioned that it began as a small serpent (hayyah) then grew in size.