Mazda does NOT want anyone but dealers doing updates.
That's unfortunate, isn't it? Even Toyota has an easy-to-update system with downloadable files that are easy to find and select-- see Toyota Downloads for example. A well-designed infotainment system would have built-in integrity checks to allow the update process to proceed safely. Mazda's way, with its bizarre update procedure and dependence on precise timing, is asking for trouble... and pissed-off customers.