spoiler: zebo battle very hard...

[sharien]

you also can use your fighters to destroy all inhibitors, avoiding enemy contacts as much as possible
the berserk armada should always follow your mothership...so just fly around in the system until all inhibitors are destroyed...
if youre not fast enough and have a save before mission...equip engine upgrades or let one of your pilots fly the mothership
and as b12... said...once those are down the mission is pretty much won