Zombine

The Zombine or Combine Zombie is the result of a headcrab attaching to a Combine Overwatch Soldier. Alyx Vance coined the term "Zombine" as a portmanteau of "Zombie" and "Combine". The appearance of the Zombine was taken as evidence that the Combine were losing control of City 17 following the near-destruction of the Citadel.

Prior to the human uprising, there were very few headcrabs in the city, only found in areas that had fallen into disrepair. However, thanks to the prolific use of headcrab shells against rebel safehouses before and during the uprising, headcrabs came to infest large areas of the city, particularly its underground sections.

Zombines are first encountered in Half Life 2: Episode One, when Gordon Freeman and Alyx Vance stumble upon a troop train in the severely headcrab infested City 17 underground, in the chapter Lowlife.

Capabilities
Zombines walk more slowly than the average Zombie, however, Zombines are capable of short sprints, which allow them to quickly close in on their prey.

Like the traditional Zombie, Zombines attack with their claws. However, because Overwatch Soldiers are normally equipped with grenades, a Zombine will, on occasion, take out a live grenade and attempt to club its target with it. Apparently, Zombines are no longer aware of a grenade's proper function, and will continue to hold on to their grenade until it detonates, killing them and anything else in close vicinity.

The combination of the Zombine's bloodied yet mostly intact body armour, and the fact that Headcrabs are able to boost their host's endurance against damage, allows Zombines to take a lot of damage.

Zombine groans are filtered through the soldier's vocoder. This "speech" consists not only of Zombie growls but also Combine soldier reports, such as "Necrotics inbound" or "Sector's not secure", suggesting that the host is somewhat aware of what it is doing.

It is interesting to note that the removal of a Zombine's headcrab reveals that, aside from the lower jaw and small lower portion of skull, no head or helmet remains on the soldier's corpse.

Zombines are commonly found with other Headcrab Zombies.