What is the difference between wazifa and zhikr?

Wazifa in Arabic means "duty" or "daily ration" while Zhikr in Arabic means "remembrance" or "recollection" (of God, to be specific). To "do" zhikr tends to mean reciting the Names of God (either collectively or individually). On the other hand, the Sufis have defined wazifa as reciting or meditating upon the Names of God to better bring them into one's life. Isn't that what you "do" in zhikr anyways? How are these two "practices" different from one another (if they are)?