Zeros is a shorten term to relate to zero dividend preference shares. These share are just the same as any other preference share with one main difference, unlike ordinary preference shares they do not pay dividends. At the end of the zero dividends preference share life one lump sum is paid out.
This make Zeros very similar to zero coupon bonds but are much riskier. If a company struggles to make it payments bonds are paid out before share. This means a higher percentage of Zeros fail to mature then bonds making them riskier.
Zeros are very susceptible to changes over their lifespan. Zero dividend preference shares pay a single sum at the end of a set period of time, due to the length of time that passes until the payment is made a slight change in the risk premium could cause a considerable change in value.