Unfortunately not a lot of changes in this release, here’s the release announcement from Zorin OS group:
The Zorin OS Team are pleased to announce the release of Zorin OS 6.3 Core, our operating system designed for Windows users. Zorin OS 6.3 builds on top of our popular previous release of Zorin OS 6.2 with newly updated software and a newer kernel out of the box. As Zorin OS 6.3 is based on Ubuntu 12.04 it is an LTS (Long Term Support) release, provided with software updates until April 2017.
Users who already have Zorin OS 6, 6.1 or 6.2 Core installed can update their system using the Update Manager to avail of the aforementioned updates and improvements in 6.3.
As usual I am mirroring Zorin OS at this address (only 64 bit “core” edition), see: