You did a factory reset? OK, that wipes everything, so explains the data loss.
If you have an external backup, such as if you enabled the option to let Google back your device up, you may have a chance. If you didn't then it's not good: unless the game data were saved in a usb mass storage mountable partition (does the Z tablet let you mount your tablet's storage that way?) you'd probably need professional forensic tools to do this.