Zaros was very clear that his sentimentality would stop him from doing the job with his own hands, but asking others to do it was acceptable. Zaros is a very calculating and strategic person.
He knows what must be done for the common good and that is to eliminate Lortad. Now, he does not feel capable of doing it, especially since it would be difficult to stop Lortad if he planned to escape since they possess similar strength, so he needed someone else to do it.
Although he could accomplish the task with the help of Elidyr, who is relatively close, it would be difficult if he is not fully committed, and he knew that he is not, so he also called Arion and Lugia.
With that alignment, it was difficult for Lortad to escape, unless something changed radically, but for the moment it was the best plan. Arion and Lugia at that time were in Arion's hidden village and when they received the news, they left immediately.
