[tex]\frac{\partial^2 u}{\partial x\partial y}=\frac{\partial z}{\partial y} =x\exp(2y)\exp(x\exp(y))+\exp(y)\exp(x\exp(/tex]
[tex]\frac{\partial^2 u}{\partial x\partial y}=\frac{\partial z}{\partial y} =x\exp(2y)\exp(x\exp(y))+\exp(y)\exp(x\exp(/tex]