Master integrals for $e^{+}{e}^{-}\to 2\gamma$ process at large energies and angles

We calculate two-loop massive master integrals for $e^{+}{e}^{-}\to 2\gamma$ in terms of generalized power series with respect to electron mass. The coefficients of this series are expressed via Goncharov’s polylogarithms. Our approach exploits a number of modern multiloop methods: IBP reduction, differential equations for master integrals, Frobenius method, reduction to $\epsilon$-form, and DRA method.