  Upcoming Sunyaev-Zel'dovich surveys are expected to return ~10^4 intermediate
mass clusters at high redshift. Their average masses must be known to same
accuracy as desired for the dark energy properties. Internal to the surveys,
the CMB potentially provides a source for lensing mass measurements whose
distance is precisely known and behind all clusters. We develop statistical
mass estimators from 6 quadratic combinations of CMB temperature and
polarization fields that can simultaneously recover large-scale structure and
cluster mass profiles. The performance of these estimators on idealized NFW
clusters suggests that surveys with a ~1' beam and 10uK' noise in
uncontaminated temperature maps can make a ~10sigma detection, or equivalently
a ~10% mass measurement for each 10^3 set of clusters. With internal or
external acoustic scale E-polarization measurements, the ET cross correlation
estimator can provide a stringent test for contaminants on a first detection at
\~1/3 the significance. For surveys that reach below 3muK', the EB cross
correlation estimator should provide the most precise measurements and
potentially the strongest control over contaminants.
