To download and name the .zip folder you will need saveAs() from file-saver

import { saveAs } from "file-saver";

  zip
    .generateAsync({
      type: "blob"
    })
    .then(content => {
      saveAs(content, "fileName.zip");
    });

As the zip creation is async the code handling it also needs to be async. Make your createURL handler async and await the zip inside of it:

const createURL = useCallback(async (node, reportHeight, reportWidth, imgHeight) => {
    try {
        const dataUrl = await domtoimage.toJpeg(node, {width: reportInViewerRef.current.offsetWidth, height: reportInViewerRef.current.scrollHeight})
    } catch (error) {
        return console.error('oops, something went wrong!', error);
    }

    // ... you can use dataUrl from here

    let base64pdf = await getZip(btoa(fileName, pdf.output()));

    // ... do something with the zip file
}

Generally speaking if an async function returns something the code using it also needs to be async.