PbCuTe2O6 offers the first opportunity to study a 3D quantum spin liquid well modeled by the simple Heisenberg Hamiltonian on a highly frustrated lattice coined "hyper-hyperkagome". The high purity of the parent compound allows for long sought refined studies like the response to well controlled spin vacancies. To investigate the effect of such perturbation to the spin dynamics and the ground state, we propose to measure the relaxation in non-magnetic Zn doped PbCu1-xZnxTe2O6 samples.