C#/ExtJs SharpZilLib generate a corrupted zip

Question

I'm using the library SharpzipLib to create a zip file from files in a memory stream. The issue is that the generated zip seems to be corrupted and I can't open it.

        MemoryStream outputMemStream = new MemoryStream();
        ZipOutputStream zipStream = new ZipOutputStream(outputMemStream);

        zipStream.SetLevel(3); //0-9, 9 being the highest level of compression

        // loops through the PDFs I need to create
        foreach (var file in files)
        {
            var newEntry = new ZipEntry(file.FileName);
            newEntry.DateTime = DateTime.Now;

            zipStream.PutNextEntry(newEntry);

            byte[] bytes = file.Content;

            MemoryStream inStream = new MemoryStream(bytes);
            StreamUtils.Copy(inStream, zipStream, new byte[4096]);
            inStream.Close();
            zipStream.CloseEntry();
        }

        zipStream.IsStreamOwner = false;    // False stops the Close also Closing the underlying stream.
        zipStream.Close();          // Must finish the ZipOutputStream before using outputMemStream.

        outputMemStream.Position = 0;

        stream.Seek(0, SeekOrigin.Begin);
        var httpResponseMessage = new HttpResponseMessage(HttpStatusCode.OK)
        {
            Content = new StreamContent(stream)
        };

        httpResponseMessage.Content.Headers.ContentType = new MediaTypeHeaderValue(contentType);
        httpResponseMessage.Content.Headers.ContentLength = stream.Length;
        httpResponseMessage.ContentDisposition =
                new ContentDispositionHeaderValue(asAttachment ? DownloadAttachment : InlineAttachment)
                {
                    FileName = fileName,
                    Name = fileCaption
                };

Files contain a list of objects with a byte[] from a pdf and a name. If I download the files individually they are fine.

TargetfileName looks like this: testFile-2023-01-02-18-02-23.zip

I tried with asAttachement as true and false.

Here's how the file is downloaded on the front end :

    var zipName = "TestFiles-" + new Date() + ".zip";
    let viewModel = this.getViewModel(),
        url = "localhost:10000/Documents/File?" + "ids=" + docIds.join(",") + "&fileName=" + zipName;
    Ext.Ajax.request({
        url: url,
        method: 'GET',
        useDefaultXhrHeader: false,
        withCredentials: true,

        success: function(response, options) {
            if(response.status == 200) {
                var a = document.createElement("a");
                document.body.appendChild(a);
                a.style = "display: none";
                var blob = new Blob([response.responseBytes || response.responseXml || response.responseText], {type: 'octet/stream'});
                var windowUrl = window.URL.createObjectURL(blob);
                a.href = windowUrl;
                a.download = zipName;
                a.click();
            }
        }
    });

It's ExtJS but I did a simple ajax request. I don't know if I did something wrong in the back-end or the front end.