@react-leaflet/core/lib/grid-layer.js

React Leaflet core

export function updateGridLayer(layer, props, prevProps) {
    const { opacity, zIndex } = props;
    if (opacity != null && opacity !== prevProps.opacity) {
        layer.setOpacity(opacity);
    }
    if (zIndex != null && zIndex !== prevProps.zIndex) {
        layer.setZIndex(zIndex);
    }
}