Statement -I: ${\left[{\mathrm{CoF}}_6\right]}^{-3}$ is diamagnetic while ${\left[\mathrm{Co}{\left({\mathrm{C}}_2{\mathrm{O}}_4\right)}_3\right]}^{-3}$ is paramagnetic

Statement -II:  Crystal field splitting in ${\left[{\mathrm{CoF}}_6\right]}^{-3}$ is more than crystal field splitting in ${\left[\mathrm{Co}{\left({\mathrm{C}}_2{\mathrm{O}}_4\right)}_3\right]}^{-3}$

${\left[{\mathrm{CoF}}_6\right]}^{-3}$ is paramagnetic because F^- is weak field ligand

${\left[\mathrm{Co}{\left({\mathrm{C}}_2{\mathrm{O}}_4\right)}_3\right]}^{-3}$ is diamagnetic  because oxalalte ligand is strong field ligand

strong field ligand brings more crystal field splitting(oxidation number of metal ion is same)