Breaking In
The moment that Henry charged forward, he did not even take his time to focus on the gold rank zombies that had already been attracted by his movements. Instead, he simply focused on the barrier, that was supposed to be behind those zombies.
It was true that he could not see where the barrier was actually, but still, he could identify that it was definitely behind the zombies due to the movements of the zombies, and the way that they looked back from time to time.
The moment that the zombies began moving forward with the intention of attacking and stopping Henry from reaching the barrier, several attacks rained down on them, easily decimating them.
Of course there was no way that the zombies in the gold rank could survive attacks from those that had already reached the diamond rank. So, the moment that the attack landed on them, they were easily dealt with.