It's smooth halving every 4 years.

We have the same halving like bitcoin and many other coins: Every 4 years there will be half as many coins per block.

So in 2022, a ZETTEL block will issue just 5 ZETTEL.
In 2026 it will be just 2.5 ZETTEL per block,
etc

Only that we get to that point in a smooth way, slightly reducing the amount per block with each step, instead of abruptly reducing it by half every 2 Million blocks.