zoom.css

.zoom-img_wrap {
    position: relative;
    overflow: hidden;
    width: 600px;
    height: 600px;
}

.zoom-img_wrap img {
    position: absolute;
    width: auto;
    height: auto;
    left: 0;
    right: 0;
    top: 0;
    bottom: 0;
    max-width: 100%;
    max-height: 100%;
    cursor: grab;
}

.zoom-img_wrap img:active {
    cursor: grabbing;
}

.btn-zoom-in,
.btn-zoom-out {
    position: absolute;
    display: inline-block;
    width: 38px;
    height: 38px;
    bottom: 0;
    border: 0;
    border-radius: 0;
    background-color: grey;
    cursor: pointer;
}

.btn-zoom-in::before,
.btn-zoom-in::after,
.btn-zoom-out::before,
.btn-zoom-out::after {
    content: '';
    position: absolute;
    top: 18px;
    left: 12px;
    display: block;
    width: 14px;
    height: 1px;
    border-bottom: 2px solid white;
}

.btn-zoom-out {
    right: 38px;
}

.btn-zoom-in {
    right: 0;
}

.btn-zoom-in::after {
    transform: rotate(90deg);
}