Death star alpha Strike.
My strategy is to create a way point. Send all my constructors to that point. I thinks its 8 but Peace may be right at 7.
Package them in fleets of 8 and send them to enemy star systems. When all in place. The enemy never seems to mind when your at peace with them.
Save game because sometimes it crashes at this point.
Build your star bases right up against the planets. Make sure you got lots of money. Is it 5000bc per Death Star now? It changed.
Once built you need to wait one turn. Save game, then Destroy every system in one turn. Its a beutiful sight to behold.
Meet with alien in diplomacy screen and make peace with him again even though he is wiped out. This way if he has any allies they won't declare war on you.
Nothing says revenge like the Death Star Alpha strike.