  A prospective measurement of the differential cross section of \tWZ
production with respect to the transverse momentum of the \PZ boson using a
general-purpose detector at the High-Luminosity Large Hadron Collider (HL-LHC)
is described. The response of a general-purpose detector at the HL-LHC is
simulated and used to estimate the uncertainties and covariances of the
differential cross section measurement. Constraints on the Standard Model
Effective Field Theory (SMEFT) enabled by the measurement are estimated. A
parametric model of the differential cross section in the SMEFT is constructed
and is used to determine the expected posterior probability function of six
SMEFT Wilson coefficients and the expected 95\% Bayesian credible intervals for
each coefficient and pair of coefficients. The intervals suggest that for all
coefficients, the measurement will provide competitive but weaker constraints
than those derived from other \mbox{HL-LHC} measurements involving top quarks
and \PZ bosons. However, as the measurement is simultaneously sensitive to to a
unique set of SMEFT coefficients, it will provide a useful input to a global
SMEFT analysis that considers many operators.
