  The Fermilab Lattice and MILC collaborations have shown in one-loop lattice
QCD perturbation theory that the renormalization constants of vector and
axial-vector mixed clover-asqtad currents are closely related to the product of
those for clover-clover and asqtad-asqtad (local) vector currents. To be useful
for future higher precision calculations this relationship must be valid beyond
one-loop and very general. We test its validity nonperturbatively using clover
and Highly Improved Staggered (HISQ) strange quarks, utilising the absolute
normalization of the HISQ temporal axial current. We find that the
renormalization of the mixed current differs from the square root of the
product of the pure HISQ and pure clover currents by $2-3\%$. We also compare
discretization errors between the clover and HISQ formalisms.
