We investigate Lp boundedness
of zonal multipliers on the 2n + 1-dimensional Heisenberg group Hn. These are
multipliers which are invariant under the group SU(n) acting in the noncentral
variables. The result is then applied to derive sufficient conditions for Lp
boundedness for a class of multipliers associated with SU(n) invariant operators in
the enveloping algebra of Hn. A necessary condition is also obtained with the aid of
group contractions.