Chapter 5 - Section 5.3 - Special Products - Exercise Set - Page 367: 30

$25z^2-4$

Using $(a+b)(a-b)=a^2-b^2$ or the special product of the sum and difference of like terms, the product of the given expression, $ (5z-2)(5z+2) ,$ is \begin{array}{l}\require{cancel} 5z(5z)-2(2) \\\\= 25z^2-4 .\end{array}