I *think* I'm actually going to be able to win this.
For those interested, here are the details:
First, I updated to the latest beta and sure enough, when I release wasps on the HW, the cockroaches get killed as well (this seems a bit intermittent though, sometimes it would work, sometimes it wouldn't. In order to actually make use of it, I had to make liberal use of save/load. I'm not sure if this is intentional or not..)
I took the world that had the colony rebellion as I didn't think I had a chance of winning before the time was up and there was no way I'd survive an extra 100 AIP + another 100 AIP from a HW death for long. (with the extra K, I got raid starships Mk 3)
Then I considered what it was that I needed to achieve and what I needed to deal with in order for that to happen.
Targets:
1. Neinzul spawners - they are somewhat mitigated by my hive golems but are still a big headache.
2. Other guard posts.
3. Ships and reserves.
4. Raid engine
5. Force fields, fortress and command center.
Things that needed to be overcome in order to damage the targets:
1. Core world forces and any reserves that spawn.
2. Raid engine hit on core world from HW.
3. Raid engine hit on HW from other core world.
4. Neinzul cockroaches from the spawn posts.
I also need more ships to deal some damage and soak up the incoming fire. I'm already using everything I have, I can spare some ships here and there but I think I'll need more. I find there are mk 3 and 4 zenith reserves fairly close to my borders so organise a strike force to hit these worlds and grab the ships.
I also add the strongest ships from my 2 defensive fleets and finish building all the ships I possibly can.
Eventually, I'm ready to give it a go:
The key is the hive golems. First, I release one set of 500 wasps on the core world. This is enough to deal with the forces there and the (relatively) small amount of reserves that the AI has over it's 70% limit.
I move my ships closer, but not to close, to the HW wormhole and wait. When the raid hits, release the second set of wasps and take my ships through to the HW.
I immediately send my raid starships to hit the closest neinzul spawner and the bomber starships to hit a close guard post.
my other ships hang around the wormhole and shoot stuff lots. I've only got 1 min until the second raid engine forces arrive and I have slow ships so don't want to get caught out.
When the roaches spawn, I release the 30-40 wasps my hives have built up - bye bye 3,000 roaches
With the targets destroyed, I retreat and group move everything back to my staging area (the planet I took that had a colony rebellion). I release a final burst of wasps on the core world to slow down the 1,000 odd ships from the second raid engine that are chasing me back.
When I'm up to about 100-150 wasps each in the hives, I move my ships the other way out of my staging system to get the AI to attack and then move back in. The wasps soften up their forces and the rest of my ships finish the job. (I keep the irreplaceable neinzul reserves out of this fight)
Now it's time for lots of repair and rebuilding. Once I'm back to 400+ wasps each, it's time to go in again. Repeating this process 3 or 4 times, most of the guard posts are dead and I'm ready to take on the reserves.
This means staying on the HW longer, so I have to deal with the second raid engine spawn more directly. I find the best tactic is to go in, sit around the wormhole and just let the reserves attack me for a minute. When the raid forces arrive, I duck back out to the core world, destroy them as the come through and then dive back in to the HW to take out some more reserves. It's become a real war of attrition but I'm getting the better of this bastard slowly but surely.
Respawn rate of reserves are definitely not keeping up with my attacks and soon I think I'll be able to commence the final phase of operation 'oh my god, when will it end'.
Of course while all this is going on, I have to deal with all the usual waves attacks all over and constant attrition on my beachead world (special forces pass through there regularly). Essentially, all I have to counter this stuff is the botnet golem and the left overs of my fleet ships.
This means I've done a fair bit of save/reload after getting a wave attack that I know I wouldn't be able to deal with. The worst are neinzul vultures, parasites (around 5000 in a wave from the vicious raider. cruicially, they are immune to reclamation), space planes (again, about 5000 in a wave. In order to get close enough, my botnet golem is pretty much alpha'd by their damage) and bombards (about 500... seriously, 500 bombards popping out of a wormhole is enough to alpha pretty much everything). By contrast, waves of things like bombers, fighters, electric bombers all make fodder for my zombie army and while others such as missile frigates and raiders are more challenging, they can be dealt with too.
I'm up to about 28 hours played now and my actual game time is over 10 hours higher. (Looks like I still won't get that 36 hour achievement... with luck I never will
Thanks for all the advice on here. Once more, into the abyss!