Solution - Simplification or other simple results

Step  1  :

            x13
 Simplify   ———
             2 

Equation at the end of step  1  :

   d   x13
  —— • ———
  dz    2 

Step  2  :

             d
 Simplify   ——
            dz

Canceling Out :

 2.1    Canceling out d as it appears on both sides of the fraction line

Equation at the end of step  2  :

  1   x13
  — • ———
  z    2 

Step  3  :

Final result :

  x13
  ———
  2z