Which one of the following reactions of Xenon compounds is not feasible?

${\text{XeF}}_6$ reacts with water to form ${\text{XeO}}_3$ (hydrolysis), but the reverse reaction of ${\text{XeO}}_3$ with $\text{HF}$ to form ${\text{XeF}}_6$ is not feasible as ${\text{XeO}}_3$ is a stable end-product of hydrolysis and the formation of ${\text{XeF}}_6$ from its oxide requires more specific and extreme conditions.