Handbook of ROCOR Liturgical Practice:

When multiple priests concelebrate the Divine Liturgy, who says the threefold Cherubic Hymn and the Prayer of the Third Hour with uplifted hands?

When priests concelebrate, only the senior priest prays the threefold Cherubic Hymn and the Prayer of the Third Hour with uplifted hands, at their appointed place in the Divine Liturgy. He repeats them thrice, in the normal way, with the deacon(s) sharing the refrains as prescribed.

In some other traditions, the threefold Cherubic Hymn and Prayer of the Third Hour are ‘shared’ between concelebrating priests (as is rightly done by concelebrating Bishops); this is not the practice of the ROCOR, and is not blessed to be done in this way in our Diocese.