To make it easy I am categorizing this in two groups. One is (xz^3), late us name it A and the other is after the multiplication sign that is (4x^4z^5) which we are naming B. Now 4 from b multiplies 1 from a(as there is no number which means there must be 1). In multiplication of power of bases we have to add the powers which means x from a × x^4 from b= x from a's power 1 + x from b's power 4=x^5 and repeating same process in case of z resulting in z^5.
