by Matteo Scaramuccia.
Hi Eugene,
Have you already tried https://docs.moodle.org/26/en/Backup_and_restore_FAQ#Using_the_new_backup_format_.28experimental.29 ?
Unfortunately for Windows, the issue here is that your PHP is still 32 bit and you have issues with its zip library. Nice explanation: http://lewiscarr.co.uk/2013/03/large-backups-fail-moodle-2/. Tech details: MDL-41838.
HTH,
Matteo