Found probs easier method, lol, why didnt I think of this earlier. Delete changes in .csc and open _zombiemode.gsc. Search for:

	if(IsDefined(level.eggs) && level.eggs !=1 )
	{
		if(level.powermusic == 0 )
		{
			setmusicstate("round_begin");
		}
		else if(level.powermusic == 1)
		{
			setmusicstate("round_begin_long");
		}
	}

Change it to:

	if(IsDefined(level.eggs) && level.eggs !=1 && level.first_round == false)
	{
		if(level.powermusic == 0 )
		{
			setmusicstate("round_begin");
		}
		else if(level.powermusic == 1)
		{
			setmusicstate("round_begin_long");
		}
	}