Zion and Jerusalem both refer to the same place here: they both refer to where the Lord has his dwelling place with his people. That place, we could say, is his centre of gravity! With his people—that is where he wants to be. This also means that what happens to his people in this world really matters to him. It might not always appear to be that way, but it is. In his wisdom he might allow things to go on for a while—even for years, or a lifetime—but still, he really cares. If anything will prompt him to roar in wrath it is the mistreatment of his people who seek him and cry out to him.