  Besides structure function measurements and jet physics, there is a lively
collection of more specific QCD analyses at HERA. In this contribution we
present three-jet angular correlations and subjet distributions measured in ep
collisions with the ZEUS detector. The angular correlations provide sensitivity
to the color factors of the underlying gauge group and thus facilitate tests of
basic properties of the strong interaction. The subjet distributions allow
tests of the QCD radiation pattern within a jet in the perturbative regime.
