The basic character of hydroxides decreases from $\mathrm{L}\mathrm{a}{\left(\mathrm{O}\mathrm{H}\right)}_3$ to $\mathrm{L}\mathrm{u}{\left(\mathrm{O}\mathrm{H}\right)}_3$. Due to smaller size of $\text{Lu,}$ the $\text{Lu}-\text{OH}$ bond attains more covalent character.
Also, due to Lanthanide contraction ${\text{Zr}}^{\text{4+}}$ and ${\text{Hf}}^{\text{4+}}$ possess almost the same ionic radii.
${\text{Ce}}^{\text{4+}}$ is a strong oxidant.