Retarder in zinc oxide eugenol is
Setting Time and Factors Affecting ZOE:
The normal reactivity between zinc oxide and eugenol is very limited and must be accelerated in order for the material to have a practical clinical application. Acceleration of the set may be achieved by:

Incorporating chemical accelerators in the mix (the most efficient and predictable way of controlling the setting time).
Reducing the powder particle size, providing for accelerated reactivity.
Increasing the powder: Liquid ratio (of limited effect in reducing the setting time).
Increasing the percentage of rosin and fillers.
Increasing the temperature and/or humidity.
Adding water to the original mix or after mixing is complete and seated into the preparation.
Introducing greater energy in the mixing procedure (pressure-movement and time).

A delay in setting is rarely needed. This is accomplished by adding vegetable oils or glycerin which keep the mass plasticized for a long period of time.
Ref: Marzouk’s operative dentistry page no 263
CaCl2
Zinc acetate
Alcohol
Glycerine