map.on('zoom', function(){
    var z = map.getZoom();
    if (z > 0 && z < 8) {
        return carto.addTo(map);
    }
    if (someManualControlIsActive) {
        return carto.addTo(map);
    }
    return carto.removeFrom(map);
});

https://gis.stackexchange.com/questions/182657/zoom-dependent-layers-in-leaflet