It's fairly easy - you just need to know what to fire at and when.
Google for a walkthrough and you'll find out how easy it is.
You hide behind some cover, and at certain moments, pop up and nuke the
left and right ship gun turrets, then you fire one through a hatch in the
middle and it's all over. You only need the tactical nuke, so don't bother
firing any conventional weapons at it.