Answer
The GCF is 7$z^{2}$
Work Step by Step
14$z^{4}$-42$z^{3}$+21$z^{2}$
Find prime factors of each term:
14$z^{4}$=2$\times$7$\times$z$\times$z$\times$z$\times$z
42$z^{3}$=2$\times$3$\times$7$\times$z$\times$z$\times$z
21$z^{2}$=3$\times$7$\times$z$\times$z
Thus, the Common factors are 7$\times$z$\times$z=7$z^{2}$.
