Complex sentence: Chris Mara (played by Christopher King) is one of Gus Fring's henchmen and Mike Ehrmantraut's errand runners, who runds errands among Fring, the mules, and the dealers.
Split into simpler sentences: Chris Mara (played by Christopher King) is also one of Gustavo "Gus" Fring's henchmen. He is one of Mike Ehrmantraut's errand runners between Fring, the mules and the dealers.