Given the velocity v = 5t2 − 10t.

This gives two possible values for $t$:

$$5t = 0 \implies t = 0 \text{ s}$$ $$t - 2 = 0 \implies t = 2 \text{ s}$$

The velocity is zero at $t = \boxed{\text{0 s or 2 s}}$.

The acceleration $a$ is given by $a = \frac{dv}{dt}$.

$$a = \frac{d}{dt}(5t^2 - 10t)$$ $$a = 10t - 10$$

$$10t = 10$$ $$t = \frac{10}{10}$$ $$t = 1 \text{ s}$$

The acceleration is zero at $t = \boxed{\text{1 s}}$.