  $^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr+$^{96}_{40}$Zr collisions at
$\sqrt{s_{_{\rm NN}}}=200$ GeV provide unique opportunities to study the
geometry and fluctuations raised from the deformation of the colliding nuclei.
Using iEBE-VISHNU hybrid model, we predict ${\rm ac}_{2}\{3\}$ ratios between
these two collision systems and demonstrate that the ratios of ${\rm
ac}_{2}\{3\}$, as well as the ratios of the involving flow harmonics and
event-plane correlations, are sensitive to quadrupole and octupole
deformations, which could provide strong constrains on the shape differences
between $^{96}$Ru and $^{96}$Zr. We also study the nonlinear response
coefficients $\chi_{4,22}$, which show insensitivity to the deformation effect.
