Charging speed is affected by numerous factors. The most significant of these is the power output of the charger.
Charging at a public charging point (Type 2)
Charging power at a public charging point with a Type 2 connector varies, but typically it is 22kW. With a 22kW charger the added range of a Renault Zoe in an hour is between 100 and 200 km. Charging power during the charging process is adjusted automatically and you can not influence it in any way.
Charging an electric car can be compared to pouring water to an empty glass.
When the glass is empty, you have to pour slowly so that the water does not spill over the sides of the glass (i.e. charging is slow when the battery is empty). When the glass is not empty or nearly full, you can pour more water (i.e. charging is faster when battery is charged between 20% to 80% of max capacity). When the glass is starting to get full you must gradually start to pour less and less water (i.e. charging slows down significantly when battery is almost full).
Charging at home
Charging power when charging at home from a regular Schuko connector can vary depending on the used charging cable (some have built-in restrictions), the charger in the car (that converts AC to DC) and the size of the fuse. Typically, with Renault Zoe the power range is between 2.3kW - 3.7kW.
Charging speed also depends on the temperature of the battery. Cold battery charges up slower. Thus during the cold winter months the battery charges faster in warm parking garages.
The charging time can be estimated using this calculator.