  We conjecture a new ordinary differential equation exactly isospectral to the
radial component of the homogeneous Teukolsky equation. We find this novel
relation by a hidden symmetry implied from a four-dimensional $\mathcal{N}=2$
supersymmetric quantum chromodynamics. Our proposal is powerful both in
analytical and in numerical studies. As an application, we derive high-order
perturbative series of quasinormal mode frequencies in the slowly rotating
limit. We also test our result numerically by comparing it with a known
technique.
