If the following TreeView properties are not the default value when you zoom the TreeView, the TreeView.Size or TreeView.Font property value will not change. The TreeViewZoomPolicy will help you change these value in this case.
Note: In order to change the TreeNode.NodeFont property value, TreeViewZoomPolicy will enum all nodes of the tree. If the tree has a lot of nodes, it may cause a performance issue. To avoid this problem, you can change the "Enabled" property of TreeViewZoomPolicy to False.