  A search for an exotic decay of the Higgs boson to a Z boson and a light
pseudoscalar particle (a), decaying to a pair of leptons and a pair of photons,
respectively, is presented. The search is based on proton-proton collision data
at a center-of-mass energy of $\sqrt{s}$ = 13 TeV, collected with the CMS
detector and corresponding to an integrated luminosity of 138 fb$^{-1}$. The
analysis probes pseudoscalar masses $m_\mathrm{a}$ between 1 and 30 GeV,
leading to two pairs of well-isolated leptons and photons. Upper limits at 95%
confidence level are set on the Higgs boson production cross section times its
branching fraction to two leptons and two photons. The observed (expected)
limits are in the range of 1.1-17.8 (1.7-17.9) fb within the probed
$m_\mathrm{a}$ interval. An excess of data above the expected standard model
background with a local (global) significance of 2.6 (1.3) standard deviations
is observed for a mass hypothesis of $m_\mathrm{a}$ = 3 GeV. Limits on models
involving axion-like particles, formulated as an effective field theory, are
also reported.
