It's all a matter of getting the bunker stations and keeping them from getting them.
first off, get the flak drone and nearest bunker station. If you can, trap the carrier while it's neutralising it and get rid of it as well. Next off, capture the other bunker station. If at any time the Cantharans get hold of a bunker station, kill it immediately whatever your forces. Once you have 2 bunker stations, you can win by sheer amount of ships. 3 gunships and about 3 cruisers should be enough to storm their home planet.
On a side note, may I just register how disappointed I am at the number of responses this board is getting of late. Now I know it's not because there's nothing to post about, but people can't be f***ed posting.