Complex sentence: He had Shangguan draft an edict, but as Shangguan was doing so, Empress Wu received news of what was happening, and she went to him to plead her case, as he was holding the edict that Shangguan had drafted.
Split into simpler sentences: He had Shangguan draft an edict, but as Shangguan was doing so Empress Wu received news of what was happening. She went to the emperor to plead her case, just as he was holding the edict that Shangguan had drafted.