The application - Zs Calculator - does not require permissions to any confidential information. It is simply a calculator. Numbers that are entered, and answers generated are not stored anywhere and are not visible to the app developer. As part of Google Play, the number of crashes are visible to the developer, but this is anonymous data, and precise locations and device types are invisible. The only thing known is the version of android running the application. This is presumably for bug fixing.
Ads are generated using Google Admob, and no part of the code used in the application uses user browsing history or similar to target ads to the user.