Creating new buttons and removing default ones - Openlayers-3

To change zoom buttons:

map.addControl(new ol.control.Zoom({
    className: 'custom-zoom'
}));

CSS, this is up to you:

.custom-zoom{
    bottom: .5em;
    left: .5em;
}
.custom-zoom button{
    background-color: rgba(40, 40, 40, .7);
    border-radius: 50%;
}

To create new controls: Openlayers simple custom control example

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