I'm certainly not a Viktor main so don't take my opinion with too much regard.
However, I would think that Lich Bane is a very important item for him.
I honestly think if you need to add Abyssal Scepter, replace Void Staff. I'm assuming that you are valuing the CDR and MR over the AP and Magic Pen. If not, and you wouldn't mind trading 10% CDR for being able to hold on to some of that Magic Pen. swap your Boots of Lucidity out for Sorcerers Shoes.
As for Zhonia's Hourglass, I would say if you feel like you need this, you might be better off not picking up Rabadon's Deathcap. In my opinion, Deathcap is an item that you get when you are ahead and need an offensive item to close the game. Zhonia's is more for when you are behind or even and are worried that your enemies will out scale you.