this code is a mess man ._. theres a method to do what you want using zombiemode_spawner and it only takes 10 lines of code

The reason for this based on your script is it waits for all the zombies to die. Ill work on a script to hopefully fix this if you would like.

I don't know what you have ice_radius defined to so just add that somewhere in function. This should work if not just let me know and I can try to adjust it a bit. Made basically off of your script.
Also don't worry you will get the hang of coding fast. I remember trying to first code. But good luck.

Main()
{
	Place1 = GetEnt( "place1", "targetname" );
	place1 thread function( "m9" );
}

function( Weap )
{
	ice_model = GetEnt( "ice_model", "targetname" );
	KillCount = 0;//Maybe throw in while loop if it keeps running over and over otherwise here will be fine
	while( IsDefined( self ) )
	{
		ice_model hide();
		self waittill( "trigger", Player );
		CurrWeap = Player GetCurrentWeapon();
		if( CurrWeap == Weap )
		{
			self trigger_off();
			Player takeweapon( CurrWeap );
			ice_model show();
			Zombs = GetAISpeciesArray( "axis", "all" );
			for(;;)
			{
				for( i = 0; i < Zombs.size; i++ )
				{
					if( Zombs[i] IsTouching( ice_radius ) )
						Zombs[i] waittill( "Death" );
					else
						continue;
					KillCount += 1;
					if( KillCount == 3 )
						break;
					wait .05;
				}
				if( KillCount == 3 )
					break;
				wait .05;
			}
			self trigger_on();
			ice_model SetModel( "zombie_3rd_perk_bottle_doubletap" );
			self waittill( "trigger", Player );
			Player GiveWeapon( CurrWeap + "_upgraded" );
			Player SwitchToWeapon( CurrWeap + "_upgraded" );
			ice_model hide();
		}
		//If you only want to run this once add the if( KillCount == 3 ) break;
		wait .05;
	}
}

Edit: Saw a possible bug so just fixed it.

 

Like i said, use developer and developer_script. If there is a scripting error then there is a chance that it'll show with developer commands enabled.

What is ice_radius set to. What I mean by this is it in "" or is it defined like ice_radius = Whatever;
My second guess would be is it only checks Zomb[0] then stops like that but I don't believe it will do this.

ice_radius = getent("ice_radius","targetname");