Ryubusa should win this. So far we have seen him pull off more impressive sword play. If he is not faster than Zack now he will be in NGII by leaps and bounds. Only way I see Zack pulling off a victory is having god like materia. But if restricted to elemental material such as fire,earth,ice,water,lightning and wind. Would be ok. But i still say Ryu can would win. By just being more skilled and faster. Ryu strength is in the area of of zack.and zack strength is in the area os Ryubusa.
I say Ryu 67%