  We investigate an equivalence relation on Legendrian knots in the standard
contact three-space defined by the existence of an interpolating zigzag of
Lagrangian cobordisms. We compare this relation, restricted to genus-$0$
surfaces, to smooth concordance and Lagrangian concordance. We then study the
metric monoid formed by the set of Lagrangian zigzag concordance classes, which
parallels the metric group formed by the set of smooth concordance classes,
proving structural results on torsion and satellite operators. Finally, we
discuss the relation of Lagrangian zigzag cobordism to non-classical invariants
of Legendrian knots.
