Gennadius was, together with his mentor, Mark of Ephesus, involved in the Council of Florence which aimed to end the schism between East and West, and had studied and written extensively on Western theology.
Gennadius was with his mentor. This was together. This mentor was involved in the Council of Florence. This Council of Florence aimed to end the schism between East and West. This Council of Florence had studied and written extensively on Western theology. Mark of Ephesus was his mentor.