Answer
$z^{41}$
Work Step by Step
First use the exponent power rule: ($x^{y}$)$^{z}$=x$^{y\times z}$
$z^{4\times 5}$=$z^{20}$
$z^{3\times 7}$=$z^{21}$
Then use the exponent product rule: $x^{y}$$\times$$x^{z}$=$x^{y+z}$
$z^{20}$$\times$$z^{21}$=$z^{41}$
