steps to reproduce

1. run attached zul with IE11 or chrome
2. click the button to open the CKEditor
3. maximize the editor with its button on the toolbar
4. resize the browser

result

the editor shrinks to a smaller size and doesn't expand as the browser size

debug info

• it happens on ZK 6.5.0 and 7.0.7

workaround

• It's related to the window's position attribute, do not specify it or specify it with left, top or parent will eliminate this issue.

  <window position="parent">