  Magneto-oscillations in two-dimensional systems with spin-orbit interaction
are typically characterized by fast Shubnikov-de~Haas (SdH) oscillations and
slower spin-orbit-related beatings. The characterization of the full SdH
oscillatory behavior in systems with both spin-orbit interaction and Zeeman
coupling requires a time consuming diagonalization of large matrices for many
magnetic field values. By using the Poisson summation formula we can explicitly
separate the density of states into, fast and slow oscillations, which
determine the corresponding fast and slow parts of the magneto-oscillations. We
introduce an efficient scheme of partial diagonalization of our Hamiltonian,
where only states close to the Fermi energy are needed to obtain the SdH
oscillations, thus reducing the required computational time. This allows an
efficient method for fitting numerically the SdH data, using the inherent
separation of the fast and slow oscillations. We compare systems with only
Rashba spin-orbit interaction (SOI) and both Rashba and Dresselhaus SOI with,
and without, an in-plane magnetic field. The energy spectra are characterized
in terms of symmetries, which have direct and visible consequences in the
magneto-oscillations. To highlight the benefits of our methodology, we use it
to extract the spin-orbit parameters by fitting realistic transport data.
