  A planar Mott insulator with easy plane N\'eel order can be mapped onto a
Gutzwiller-projected spin Hall state. The in-plane substitution of Zn$^{2+}$
and Li$^{+}$ for Cu$^{2+}$ brings zero modes around the spin vacancy. The
Gutzwiller projection precludes single particle excitations, however, preserves
the zero modes which have a local spin moment for Zn$^{2+}$ and a local charged
hole for Li$^{+}$, respectively. While the local spin moment for Zn$^{2+}$ is
screened by the long-range spin correlations, the active charge degree of
freedom for Li$^{+}$ impurity twists the spin background with long ranged
disturbances. This proposal explains the very different roles of the Zn$^{2+}$
and Li$^{+}$ impurities on the magnetic perturbations in the CuO$_2$ plane in
the undoped cuprate compounds.
