The one zone model is one where inverse Compton scattering accelerates electrons."We applied a simple one-zone model, which could not reproduce the radio emission and the shape of the optical emission, and a two-component leptonic model with two interacting components, enabling us to reproduce the emission from radio to VHE band," the authors of the paper explained.
The two component model uses two spheroidal blobs one embedded in the other, a blob embedded in a jet. The magnetic field strengths are the same but Doppler factors differ.