  We calculate within the Extended Nambu--Jona-Lasinio model the leading in
$1/N_c$ contribution to $\gamma\gamma\to\pi^0\pi^0$ to all orders in the
external momenta and quark masses. This result is then combined with the known
two-loop Chiral Perturbation Theory and compared with the data and other
calculations. A technical difficulty in the same calculation beyond order $p^6$
for $\eta\to\pi^0\gamma\gamma$ is identified and for this decay results up to
order $p^6$ are presented.
