Complex sentence: Most ancient historians and modern scholars agree that Zenobia was displayed in the triumph in 274, Zosimus being the only one to claim that the queen died before reaching Rome, and his account regarding this event should be rejected.
Split into simpler sentences: Most ancient historians agree that Zenobia was displayed in the triumph in 274, and most modern scholars accept this. Zosimus is the only one to write that the queen died before reaching Rome, and his account regarding this event should be rejected.