Node - sequential download and zip extraction - node.js

Question

I am creating an Express server which would allow the client to receive downloaded files from different sources.
One of the file that is downloaded is a zip file, which needs to be extracted before it is send to the client. The API which is exposed to the node client has a Promise.all() to ensure that files are not send back until everything is downloaded and extracted.
// Client would call this as /download API. Once the download is completed (along with zip extraction), these files would be send to client
function download() {
return Promise.all([downloadInvoice(), downloadImages()]);
})
}).then(function (result) {
// this is happening even before the zip is extracted
console.log('content downloaded and zip extracted, send everything to client');
})
})
}
The downloadImages function calls a REST service (POST) to get images, which are then written to filesystem using pipe. Once the zip is saved in the file system, I am using extract module to extract the zip to a folder.
var req = require('request');
var extract = require('extract-zip')
function downloadImages() {
return new Promise(function(resolve, reject) {
var imageUrl = 'http://localhost:8080/restserver/downloadImages';
var postData = {
username: 'abc',
password: 'xyz'
}
var options = {
method: 'post',
body: postData,
json: true,
url: imageUrl
}
req(options, function (err, res, body) {
if (err) {
console.log('Error posting json '+err)
return;
}
console.log('Status code '+res.statusCode);
}).pipe(fs.createWriteStream('C:/temp/Images.zip'))
.on('finish',function() { // 'finish' fired as download completed. Now extract
console.log('Finished downloading Images, now extract them');
extract('C:/temp/Images.zip',
{dir: 'C:/temp/Images'},
function (err) {
if(err) {
console.log('Error extracting Images zip '+err);
}
resolve("Promised resolved for Images");
})
}).on('error', function(error) {
reject('Error extracting images', error);
});
}
}
Challenge that I am facing is that, even before zip extracts, Promise.all resolves. So, an empty folder is send to the client.
I would like things to happen in this order -
1. Promise.all in download() is used to instantiate the download
2. DownloadImages() downloads the zip of images and saves on the node server (using pipe)
3. DownloadImages() extracts the zip
4. Promise.all in download() is completed and extracted images are send to the client.
Step 3 is happening after step 4. I am not able to make out what am I doing incorrectly to chain these operations in the right sequence.