Chapter 5 - Section 5.4 - Multiplying Polynomials - Exercise Set - Page 290: 102

$-6y^{4}z^{3n}+3yz^n$

Using $a(b+c)=ab+ac$ or the Distributive Property and using the laws of exponents, the given expression, $ -3yz^n(2y^3z^{2n}-1) $, simplifies to \begin{array}{l}\require{cancel} -6y^{1+3}z^{n+2n}+3yz^n \\\\= -6y^{4}z^{3n}+3yz^n .\end{array}