9z2+36z-az-4a

Group the first two terms and the last two terms.

(9z2+36z)-az-4a

Factor out the greatest common factor (GCF) from each group.

9z(z+4)-a(z+4)

9z(z+4)-a(z+4)

Factor the polynomial by factoring out the greatest common factor, z+4.

(z+4)(9z-a)

Factor by Grouping 9z^2+36z-az-4a