Wow... Dig through older edition games and you can find a lot of weird things.

Use Barrier to boost your defense against the second earthquake. If you can manage to get it off faster than him, then great, it'll help against the first one too. Next, whip up Hailstorm, which will tear apart the clones that he makes next turn, and powers up your Blizzard.

Barrier ~ Hail ~ Blizzard