Cu-63(2) NMR linewidths in Zn-doped YBa2Cu3O7 exhibit a predominant co
mponent proportional to T-1 in the normal state. We attribute this res
ult to spin-exchange scattering of carriers from localized moments ass
ociated with Zn impurities in the CuO2 Planes. The estimated moment-ca
rrier exchange, J(eff) = 20 meV, is more than an order of magnitude to
o small to account for the suppression of T(c) in this system via Abri
kosov-Gorkov pair breaking. A suggested alternative explanation is pai
r breaking by strong potential scattering from the Zn impurity sites w
hich requires d-wave pairing.