Sorry for not getting back sooner, I3D seems to be having a slew of database and posting problems.
Anyway:
Zerstorer is an old Partial Conversion from back in 1997. It was originally created by a team known as Nihilism Unlimited.
Links for the original info and download below.
As for my plans for the upgrade mod:
Full weapons replacement. Weapons include:
Melee:
1. Knife (Rapid primary, weak, stab secondary. Does double damage from behind.)
2. Axe (Slower, but better damage. Secondary charges up a more powerful swipe. Think HL:OpForce's Pipe Wrench. Replaces the Knife.)
3. Chainsaw (Limited fuel weapon, but hidiously powerful. You cannot take this one between levels, but can capture it from defeated Ogres.)
Guns:
1. Pistol (Starting Weapon. Uses MGUN-1X Dual Core Ammo. You can throw hand grenades while using this. Also you can use two at the same time, for akimbo action!)
2. Fistgun (Captured from Ogres. Compact Machine Pistol. Insane ROF. 24 round magazine. Secondary allows you to throw it, where it then explodes. You can throw grenades, but this weapon requires two hands to properly control, so no akimbo.)
3. Shotgun (Eight round magazine. Extremely Powerful, but loses power with distance. Secondary is double shot burst. Explosive shells availible.)
And many other weapons.
Other features include multiple endings based on what you do. Performing certain actions may reveal secrets such as Turok-esque teleportals leading to other levels that contain items that are essential to your success or failure.
Monsters aren't just moron clones of each other, they now use the same weapons you do, with different variations. Who needs intelligence in an army of darkness, when you've got a monster with a rocket launcher that doesn't care if it dies, so long as it takes you with it?
Full secondary support for Painkeep maps! Double the Deathmatch Pain!
Or to be more brief, mostly regular Quake, only harder, and with weaponry that kicks more butt than the regular vanilla weapons, and other nice very nice things.
Any other more specific questions? =D