Image caption Z-index

Hello

Thank you for your help about this issue:
https://kriesi.at/support/topic/image-caption-on-logo-element/
But a I need a little help again about this.

I set .slidealt selector z-index value higher than .avia-logo-element-container .slide-image, but is not work.
How can I do that .slidealt be above the image when I hover on.

#top .avia-logo-element-container .slide-image:hover img {
   opacity: 0.6;
   -webkit-transition: all 0.4s ease-in-out;
   transition: all 0.4s ease-in-out;
}

.slidealt {
   padding: 20px;
   font-size: 16px;
   color: #222222;
   font-weight: 600;
   -webkit-transition: all 0.4s ease-in-out;
   transition: all 0.4s ease-in-out;
}

div.slidealt {
   z-index: 1000 !important;
}

a.slide-image {
    outline: 0;
    text-decoration: none !important;
}

#top .avia-logo-element-container .slide-image:hover .slidealt {
   margin-top: -20px;
   -webkit-transition: all 0.4s ease-in-out;
   transition: all 0.4s ease-in-out;
}

Best regards,
Peter