The opinion of abu hanifa is, its wrong to supplicate by means of creation.
ad -Durrul -Mukhtaar (2/630) Aboo Haneefah said : It is not fitting at all that anyone should supplicate to Allaah except by Him
Az-Zubaydee says in Sharhul-Ihyaa (2/285): "Aboo Haneefah and his two companions hated that a person should say: To ask You by the right of so and so' or ' By the right of Your Prophets and Messengers' or 'By the right of the Sacred House and Sacred Area (of Muzdalifah)' and the like, since no one has any right upon Allaah.
Opinion of Ahmad bin hanbal is one can supplicate by means of Prophet's status (prophets are creation).
"Imaam Ahmad allowed tawassul by means of the Messenger alone"
Reference: page 44, tawassul at waseelah by sk.albani.
Since both scholars cannot be correct, how do we conclude which one is correct?