Zero was very shrewd, predicting well in advance that the Time Lords would send the Doctor to investigate his sudden disappearance into exile and that he might have to stop him.
He had a very dry wit and enjoyed using jokes, for example after regenerating into one of the avian species and causing the Doctor to flee all according to his plan, he commented that he "had hit two birds with one stone".
He regenerated into one of the native avian species on the planet he was living on in his exile after dying from touching the Yolk of Dartsplant.
At some point in his life, he took up acting in Athens, as the Doctor mentions. He also had tasted senawine at some point, commenting that the Yolk of Dart tasted just like it.
Despite already having the title of Lord Cardinal, the Fifth Doctor stated that Zero was only "well on his way to getting a seat on the High Council". (AUDIO: Spring)