Is there a way to change the z-index of our chat widget?

Is there a way to change the z-index of our chat widget?

I tried uploading a css file to change the z-index of my chat widget and float button on the Change Chat Window Appearance with Custom CSS File feature but it is not working. I change it because it is overlapping our custom cookie dialog. 

.zls-sptwndw {
    position: fixed;
    display: none;
    bottom: 0;
    cursor: pointer;
    z-index: 0!important;
}
.zsiq_floatmain {
    position: fixed;
    z-index: 0!important;
    max-width: 305px;
    box-sizing: border-box;
    }