  The Large High Altitude Air Shower Observatory~(LHAASO) is one of the most
sensitive gamma-ray detector arrays, whose ultrahigh-energy~(UHE) work bands
not only help to study the origin and acceleration mechanism of UHE cosmic
rays, but also provide the opportunity to test fundamental physics concepts
such as Lorentz symmetry. LHAASO directly observes the $1.42~\mathrm{PeV}$
highest-energy photon. By adopting the synchrotion self-Compton model, LHAASO
also suggests that the $1.12~\mathrm{PeV}$ high-energy photon from Crab Nebula
corresponds to a $2.3~\mathrm{PeV}$ high-energy electron. We study the
$1.42~\mathrm{PeV}$ photon decay and the $2.3~\mathrm{PeV}$ electron decay to
perform a joint analysis on photon and electron two-dimensional Lorentz
violation~(LV) parameter plane. Our analysis is systematic and comprehensive,
and we naturally get the strictest constraints from merely considering photon
LV effect in photon decay and electron LV effect in electron decay. Our result
also permits the parameter space for new physics beyond relativity.
