There will be 21 million Zcoins. Zcoin follows the same halving cycle as Bitcoin (every 4 years). 10% of the total Zcoin supply will be distributed to the Founders Reward as time passes.
In the first 4 years, 20% of Zcoins will be distributed to the Founders Reward. In other words, during the first 4 years, 40 Zcoins will go to the miners and 10 Zcoins will go towards the Founders reward. To find out how the Founder’s Rewards are used, see here.
After the first 4 years, the block reward goes completely towards the miners.