  In this note, $\mathrm{ZHH}$ production in the all-hadronic final state is
studied in $\mathrm{e}^{+}\mathrm{e}^{-}$ collisions at the Compact Linear
Collider at the 3 TeV stage. At this stage this Higgs boson pair production
mode is sub-leading to the $\mathrm{W}^{+}\mathrm{W}^{-}$ fusion production
cross-section of $\mathrm{e}^{+}\mathrm{e}^{-}\rightarrow\mathrm{HH}\nu\nu$.
The events are characterised by a topology of six jets, where the masses of the
three pair-wise combinations of two jets are compatible with originating from
two $\mathrm{H}$ and one $\mathrm{Z}$ bosons. The event selection concentrates
on the dominant $\mathrm{H}$ boson decays into two b-quarks by requiring a
presence of multiple b-jets. The study is based on full simulation using the
CLICdet model, including beam-induced backgrounds from
$\gamma\gamma\rightarrow\mathrm{hadrons}$. Results on the measurement of the
total $\mathrm{ZHH}$ cross section are given.
