  Measurements of the differential cross sections of Z + jets and $\gamma$ +
jets production, and their ratio, are presented as a function of the boson
transverse momentum. Measurements are also presented of the angular
distribution between the Z boson and the closest jet. The analysis is based on
pp collisions at a center-of-mass energy of 13 TeV corresponding to an
integrated luminosity of 35.9 fb$^{-1}$ recorded by the CMS experiment at the
LHC. The results, corrected for detector effects, are compared with various
theoretical predictions. In general, the predictions at higher orders in
perturbation theory show better agreement with the measurements. This work
provides the first measurement of the ratio of the differential cross sections
of Z + jets and $\gamma$ + jets production at 13 TeV, as well as the first
direct measurement of Z bosons emitted collinearly with a jet.
