Heart of the Swarm- Korhal: The Reckoning (Part 2)

You will likely notice a small road to the North of Jim's base- this leads to a large Terran base that is blocking Alexei Stukov from adding his own infested Terrans to the attack.  Cripple or destroy it, and he will be allowed through, producing a large surge followed by a steady (if slow) stream of infested units that will join the fight, automatically pushing towards the main base of Augustgrad.

Around this point, the Terran Dominion will again attack your two bases, marking the time at which you should sweep back to the South and prepare to breach the Augustgrad defenses to the East.  Briefly divert some or all your assault troops to help Jim out with an attack by a pair of elite battlecruisers and some ground forces (including a couple of very nasty siege tanks), and then cut to the East- either past your own base or through Mengsk's.

The gate immediately East of your secondary base holds back Zagara's brood, and can quickly be destroyed as it is guarded by an important Terran base and a pair of bunkers, so you should face little difficulty.  This will unleash a glut of troops you can follow North, towards Mengsk's stronghold.  If you then divert to the East before actually entering the enemy base area, you can take out another Terran secondary base and break wide the area for Dehaka to come through.  The Primal Zerg unleashed by this will provide a large distraction- but not enough to prevent continued Terran attacks against your own outposts.  Make sure to keep your bases secure as best you can while you turn your attention towards the center of the map.

It is at about this time that Arcturus activates the Odin, sending it against Jim.  The massive, souped-up thor deals horrendous damage, and is accompanied by yet more elite mercenaries- it will take your entire assault force to bring the thing down.  Make sure your attackers encounter it simultaneously, as if they are strung out they will be torn apart by the large military force that the Odin is the centerpiece for.