  In this paper, we continue studying the thermodynamics of Hayward black hole,
which has been recently approached by Molina \& Villanueva regarding the laws
of black hole thermodynamics, by introducing the Hayward's parameter as being
responsible for a possible regularization of the Schwarzschild black hole.
Here, we show that the adiabatic foliations of the thermodynamic manifold are
confined by the extremal subspace, and therefore, the latter cannot be reached
adiabatically. A direct consequence of this features, is the impossibility of
the merger of two extremal Hayward black holes.
