Grr. I can get through the major portion of twilight of the gods easy. I can keep the buggers from taking over my two countries, while I kick out the guys from mine. However, what I cannot do is take over durangh to finish the game. Their forces are so overwhelming, and by the time I get control over the only country near it, I can't clear the city out to get a single tank there. It seems nigh impossible because it's usually 4 turns left by the time I trigger the event. It takes me that long to clear the two major countries. Any advice?

I don't think you're actually supposed to succeed in taking over Durghang. I think it's just something to keep you occupied while the event is triggered nd the game is finished.