Zlib data compression is already enabled on all of our Shared and Cloud hPanel hosting plans. You can double-check this, together with the main information about zlib version, on the PHP Info page:
However, zlib.outputCompression (or zlib.output_compression) PHP option is not enabled by default. To enable it, open the PHP Configuration → PHP options page, and add a checkbox for zlib.outputCompression. Make sure to save the changes!
After this, you'll be able to use zlib output compression in your projects.