Chapter R - Elementary Algebra Review - R.5 Polynomials and Factoring - R.5 Exercise Set - Page 970: 4

$(2z+5)(2z-5)$

The expressions $ 4z^2 $ and $ 25 $ are both perfect squares (the square root is exact) and are separated by a minus sign. Hence, $ 4z^2-25 ,$ is a difference of $2$ squares. Using the factoring of the difference of $2$ squares which is given by $a^2-b^2=(a+b)(a-b),$ the expression above is equivalent to \begin{array}{l}\require{cancel} (2z)^2-(5)^2 \\\\= (2z+5)(2z-5) .\end{array}