Answer
$$\frac{18y^6x}{25z^2}$$
Work Step by Step
Recall, one never divides by a fraction. Rather, if we want to divide by a fraction, we multiply by the reciprocal of the fraction. Recall, the reciprocal of a fraction is that fraction with the numerator and the denominator switched. Thus, we find:
$$ \frac{12x^2y^4}{5z}\times \frac{3y^2}{10xz} \\ \frac{18y^6x^2}{25z^2x}\\ \frac{18y^6x}{25z^2}$$
