Zack's ending
I am figuring they can't kill the Master. They will entomb him and drop in ocean as planned. Zack and all will be there and Zack will have come to his senses or so we think several episodes before the end.
However out of the blue Setrakian will behead Zack and announce that Zack has been corrupted by the Master and is a loose end that would surely set the Master free and thus must be terminated. All present are shocked and stunned, and Eph will attack Setrakian. But everyone else will side with Setrakian leaving Eph the odd man out.