lol
two zenyatta was actually part of a very powerful team comp back in beta
the reason for that is gone now, but zen isn't weak
I'd need the full story because it depends on how many support you had, but if they were the only two support, then the second zen was better than the genji just to give that second support. Also if the enemy was stacking tanks, a second zen chaos orb will help melt through them.
But if that gave you three support, then it would have been bad for that reason. Not because of the choice of class.