  We present precise predictions for prompt photon production in association
with a $Z$ boson and jets. They are obtained within the Sherpa framework as a
consistently merged inclusive sample. Leptonic decays of the $Z$ boson are
fully included in the calculation with all offshell effects. Virtual matrix
elements are provided by OpenLoops and parton shower effects are simulated with
a dipole parton shower. Thanks to the NLO QCD corrections included not only for
inclusive $Z\gamma$ production but also for the $Z\gamma$ + 1-jet process we
find significantly reduced systematic uncertainties and very good agreement
with experimental measurements at $\sqrt{s}=8$ TeV. Predictions at
$\sqrt{s}=13$ TeV are displayed including a study of theoretical uncertainties.
In view of an application of these simulations within LHC experiments, we
discuss in detail the necessary combination with a simulation of the $Z$ + jets
final state. In addition to a corresponding prescription we introduce
recommended cross checks to avoid common pitfalls during the overlap removal
between the two samples.
