64-bit versions of Raspberry Pi OS have arrived, allowing the Raspberry Pi 4 to utilise more than 4 GB of RAM natively. Raspberry Pi OS 64-bit is available to download now and is compatible with all Raspberry Pi SBCs that contain 64-bit processors, including the Raspberry Pi Zero 2.
https://www.notebookcheck.net/Raspberry-Pi-Foundation-brings-Raspberry-Pi-OS-64-bit-to-the-Raspberry-Pi-Zero-2-Raspberry-Pi-3-and-Raspberry-Pi-4.597564.0.html