This is the final mission of the game and unmissable.
*** Spoiler - click to reveal ***Your fight with Zinyak can be made easier if you complete all loyalty missions for your companions. This will result in all your friends joining the battle in the same armor your wearing. This won't do much damage to Zinyak, but it will keep the 'arena' clearer of adds. The battle with Zinyak is pretty straightforward, but I'll run it down anyway. The first damage phase is simple, dodge his attacks and damage him with everything you have. Once Zinyak puts u his shield/forcefield use Telekinesis to grab C.I.D's (small orbs) and throw them into the shield. repeat this until Zinyaks health bar is drained. The final battle is series of simle QTE's followed up by a series of cutscenes, one extra scene for the people who've done all loyalty missions.