Keep attacking with a full army of cobras. Keep them outside turret range.
His wolves will get raped and he'll have to go full (or at least mainly) cobra to stand a chance.
Then send in 10 hawks (and maybe a Vulture) and kill his cobras/turrets, then shift your cobras in and wipe the base.
Repeat with all his other bases.
If he doesn't go all cobra when you attack, he'll lose anyway and you won't even need hawks.
Hopefully this should work :D
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