The REALLY funny part is that the Xuan would be helping the whole way.
Why?
Word of Yrs, Xuanwu have a population growth dynamic similar to pandas. A Xuanwu with active elements rather than their traditional rather sleepy elements is desirable for multiple reasons.
Normal Xuanwu should be Earth and Water based, both passive, and Earth canceling out even Water's reactive portion. They'd sleep. All the time.
Zhengui being Fire and Wood based is a very very active tortoise. You wouldn't expect a baby Xuanwu to be wandering around the Outer Sect on their own, much less climbing up snowy mountains to play toboggan. That said, Zhengui almost certainly has a much bigger appetite than normal Xuanwu, as his elements compound towards Consumption and Growth.
So you know, they're probably motivated at the idea of having more Xuanwu.