place an image above revolution slider

问题:

I am trying to place an image partially above revolution slider (a part of the upper side of slider should be covered by the image) I tried with

image{position:relative;
z-index:10;
}
slider{position:relative;
z-index:1;
}

but it does not seem to work here is the link of the page: http://qebaalrabee.com/green-main/ here is how it should be:

回答1:

It might seem illogical but the solution I found is placing the image under the slider and using margin-top:-20vw;

it worked!
seems like downside elements have higher z-index