  We study the nonequilibrium quench dynamics of a mixed Sachdev-Ye-Kitaev
model, with competing two bodies random interactions leading to maximally
chaotic Non-Fermi Liquid dynamics and a single body term which dominates at low
temperatures and leads to Fermi liquid behavior. For different quench
protocols, including sudden switching of two-body interaction and double quench
protocols, we solve the large $N$ real-time Dyson equation on the Keldysh
contour and compute the dynamics of Green's functions from which we obtain
effective temperature and relaxation rates. We show that the model thermalizes
to a finite temperature equilibrium and that depending on the value of the
quench parameters the effective temperature can be below or above the
Fermi-Liquid to Non-Fermi Liquid crossover scale, which can then be accessed
through the nonequilibrium dynamics. We identify quench protocols for which the
heating dynamics slow down significantly, an effect that we interpret as a
signature of prethermalization.
