[![enter image description here](https://i.stack.imgur.com/0FGQP.png)](https://i.stack.imgur.com/0FGQP.png)

I think
Since $\nabla u\_2 \times \nabla u\_3=\dfrac{\vec{e\_1}}{h\_2h\_3} ,$ then $ \nabla\cdot(\nabla u\_2 \times \nabla u\_3)=\dfrac{1}{h\_1} \dfrac{\partial}{\partial u\_1}\bigg(\dfrac{1}{h\_1h\_2} \bigg)$
but

How is it $\nabla\cdot(\nabla u\_2 \times \nabla u\_3)=0$ ?