Z-Stoff was a name for calcium permanganate

Calcium permanganate

Calcium permanganate is an oxidizing agent. It consists of the metal calcium and two permanganate ions. It is noncombustible, but it will accelerate the burning of combustible material. If the combustible material is finely divided, the mixture may be explosive. Contact with liquid combustible...

 or potassium permanganate

Potassium permanganate

Potassium permanganate is an inorganic chemical compound with the formula KMnO4. It is a salt consisting of K+ and MnO4− ions. Formerly known as permanganate of potash or Condy's crystals, it is a strong oxidizing agent. It dissolves in water to give intensely purple solutions, the...

 mixed in water. It was normally used as a catalyst for T-Stoff

T-Stoff

T-Stoff was the oxidizer part of a bipropellant rocket fuel combination used in Germany during World War II. It is a stabilized high test peroxide...

 (high test peroxide

High test peroxide

High-test peroxide or HTP is a high -concentration solution of hydrogen peroxide, with the remainder predominantly made up of water. In contact with a catalyst, it decomposes into a high-temperature mixture of steam and oxygen, with no remaining liquid water...

) in military rocket

Rocket

A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...

 programs by Nazi Germany

Nazi Germany

Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 during World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

.

Z-Stoff was used in the cold engine of the Messerschmitt Me 163 A

Messerschmitt Me 163

The Messerschmitt Me 163 Komet, designed by Alexander Lippisch, was a German rocket-powered fighter aircraft. It is the only rocket-powered fighter aircraft ever to have been operational. Its design was revolutionary, and the Me 163 was capable of performance unrivaled at the time. Messerschmitt...

 airplane and in several early guided missiles. T-Stoff decomposed by Z-Stoff was commonly used by World War II German military to generate steam for powering of fuel pumps in airplanes and rockets.

The reaction produces manganese dioxide, which tends to clog the steam generators. Later generations used solid-state catalyst instead of its water solution. http://www.walter-rockets.i12.com/walter/me163a.htm