Complete the square and find the maximum value $ofh.$

$h(z)=-3z^2+24z+6$

Complete the square $ofh.$

$h(z)=-3(z-4{)}^2+54$

$h(z)=-(z-4{)}^2+54$

$h(z)=(z-8{)}^2-6$

$h(z)=-3(z-8{)}^2+6$

Find the maximum value $ofh.$

$(Givean$ exact answer. Use symbolic notation and fractions where needed.$)$