Slow download physical zip file on IIS 10

Question

I've tried to download physical zip file that I host on my IIS but the speed seem limited to 600KBps (or around 5mbps). The file is physical file not generated by active script (dynamic file). I've tried to eliminate some issue before asking in this Q&A:

The topology is that my Server A located on same intranet as the workstation that try to access file (Laptop B).

First thing that I check is the capability of my network on my server if it can handle more than 5mbps, I've tried to do speed test to my ISP and the upload speed result is 100mbps. By this result I know that the server network capable to upload files with speed more than 5mbps.

Second thing that I've tried is to do speed test on my Laptop B into my ISP, and the download speed result is 100mbps. So same as my server the network capable to download more than 5mbps.

From both test I know that network interface on both machine (Server A and Laptop B) capable to do 100mbps upload/download. This confirm by testing download on Laptop B large file from outside the intranet (from other website) and I got 11MBps (full bandwidth) download.

So the issue here is if both machine have network interface capable to upload/download more than 5mbps, and the zip file on my IIS server is static file not dynamic generated file, why the download cannot pass the 5mbps. If dynamic generated file this possible/customize the limit by set the content-length header, but since this is static file, there's must be a configuration on IIS that limit the transport bandwidth. I've check the max configuration (or related to content limit), all is default and all is more than 4GB settings.