(z²)/(z) = z²−1 = z

$$\frac{z^2}{z} = z^{2-1} = z$$

The simplified expression is $\boxed{z}$.

$$\frac{3x^2}{x} = 3x^{2-1} = 3x$$

The simplified expression is $\boxed{3x}$.

$$6x^2 \div x = \frac{6x^2}{x} = 6x^{2-1} = 6x$$

The simplified expression is $\boxed{6x}$.

$$\frac{5c^2}{c} = 5c^{2-1} = 5c$$

The simplified expression is $\boxed{5c}$.

$$\frac{3x^3}{x} = 3x^{3-1} = 3x^2$$

The simplified expression is $\boxed{3x^2}$.

$$\frac{2x^3}{x} = 2x^{3-1} = 2x^2$$

The simplified expression is $\boxed{2x^2}$.

$$\frac{5x^3}{x^2} = 5x^{3-2} = 5x$$

The simplified expression is $\boxed{5x}$.

$$\frac{12x^3}{3x} = \frac{12}{3} \times \frac{x^3}{x} = 4x^{3-1} = 4x^2$$

The simplified expression is $\boxed{4x^2}$.

$$\frac{18a^3}{3a} = \frac{18}{3} \times \frac{a^3}{a} = 6a^{3-1} = 6a^2$$

The simplified expression is $\boxed{6a^2}$.

$$\frac{26x^2}{2x} = \frac{26}{2} \times \frac{x^2}{x} = 13x^{2-1} = 13x$$

The simplified expression is $\boxed{13x}$.

$$\frac{33mn}{8a}$$

The expression cannot be simplified further as there are no common factors in the numerator and denominator. The simplified expression is $\boxed{\frac{33mn}{8a}}$.

$$\frac{42xy}{7y} = \frac{42}{7} \times \frac{xy}{y} = 6x$$

The simplified expression is $\boxed{6x}$.

$$\frac{54ab}{9b} = \frac{54}{9} \times \frac{ab}{b} = 6a$$

The simplified expression is $\boxed{6a}$.

$$\frac{72a^2b}{8a} = \frac{72}{8} \times \frac{a^2b}{a} = 9a^{2-1}b = 9ab$$

The simplified expression is $\boxed{9ab}$.

$$\frac{48x^2y}{12xy} = \frac{48}{12} \times \frac{x^2y}{xy} = 4x^{2-1}y^{1-1} = 4x$$

The simplified expression is $\boxed{4x}$.

$$\frac{40pq^2}{8pq} = \frac{40}{8} \times \frac{pq^2}{pq} = 5p^{1-1}q^{2-1} = 5q$$

The simplified expression is $\boxed{5q}$.