i think you need to learn more about the game before attempting something like this.
the person in your inspiration video seems to know a lot about extended hit boxes when meleeing (turning the mouse when shoving to maximize all frames to shove zombies).
and also about how spawns work. Special infected spawns less when other teammates are dead, but still spawn. they're on a timer.
if you kill zombies, more will appear in front of your path out of view. if you keep those zombies alive and rush past, there won't be any ahead until the previous ones despawn.