@Rouben Rostamian  

Thanks in advance for your fast reply, yes i konow but  i would like to change the order of integration as its important in my problem. So, i want at least to change   d\tau dz to dz d\tau

How to interchange dy d\tau dz to dz dy d\tau

@Christian Wolinski  Thanks for response, I want the interchaning of d \tau dz by dz d \tau  mathematically  not in mapple