Tess,
I am so sorry for your loss. He was a part of your family and your life will seem be different. Rely on your memories of Zeus. I had a kitty, named Pugsley, whom I had for 18 yrs and then lost. It has been several years since he died, but I still think fondly of him.
He was such a smart, mischieviuos, naughty cat with a warm personality.