Panel.ZIndex is not working controls placed on the two different Tab controls

Question

Aim: When the mouse is over on a button then the button height should become double and the button should be displayed on top of other controls. Controls can be present in 'N'number of panels or tabpages in a screen.

Actually Control placed on the Tab Control hides inside the Tab Control itself when it expands even though Panel.ZIndex = "99999".

I am using VS 2010, I have a main grid with 2 Rows. I am having 2 tab controls with buttons in my screen.

I am facing the following problems, When the mouse is over the green color button placed in a tab control.

1. Control placed on the Tab Control hides inside the Tab Control itself when it expands even though Panel.ZIndex = "99999". The expanded control is not going out of the Tab Control.

2. Control placed on the Tab control goes under the Tab Item Header when it expands.

Please check the Green color buttons in the attached solution here and give your possible solution.

Thanks in advance!