Identify the pair of lanthanoides with one strong oxidation and one strong reduction

${ }_{63}\mathrm{Eu}=\left[\mathrm{Xe}\right]4{\mathrm{f}}^{7}6{\mathrm{s}}^2$
Eu²⁺ is a strong reducing agent changing to common +3 state.
${ }_{58}\mathrm{Ce}=\left[\mathrm{Xe}\right]4{\mathrm{fl}}^{\mathrm{\prime }}5{\mathrm{d}}^{\mathrm{\prime }}6{\mathrm{s}}^2\mathrm{Ce}\left(\mathrm{IV}\right)$ is a strong $\text{oxidant.}{\mathrm{E}}^0\text{of}{\mathrm{Ce}}^{4+}/{\mathrm{Ce}}^{3+}=1.74\mathrm{V}$ The${{\mathrm{E}}_{\mathrm{r}}}^{\mathrm{o}}$ of Ce
suggests that it can oxidise water.