Answer:
2z-7
Step-by-step explanation:
[tex] \frac{6 {z}^{3} - 21z^{2} }{3 {z}^{2} } [/tex]
[tex] \frac{3 {z}^{2}(2z - 7)}{3 {z}^{2} } = 2z - 7 [/tex]