There are two problems with this quest in the journal and related dialogue topics:

• If choosing to work with Veros (TR_m3_Veros Dilthim), you still have the option to first hand in the ebony to Athryil (TR_m3_Athryil), which is fine. The problem is that if doing so, the journal entry starting with "I showed Veros the stolen ebony..." will still trigger, but that is not true, since you no longer have the ebony. The related dialogue topic does not actually say that you have shown him the ebony, but I think a difference response both in the dialogue and the journal should be in place for this situation.
• The quest is marked as finished if first handing back the ebony to Athryil, but given that you have accepted Veros's offer, the quest is still ongoing. I guess the best option is to not trigger the finishing stage under these conditions.