Question

can we call the breaking down of ozone a chemical change

Answer 1

Yes http://eco-globe.com/what-destroys-the-earths-ozone-layer/

Answer 2

Due to the recent global warming and pollution,our planet's atmospheric ozone layer is constantly breaking down.

Greenhouse gases like CO2 or CFC are the main reasons behind this ozone decomposition process.

In this decomposition process ozone turns into smaller oxygen molecules.

That's why this is a chemical change.