If you are downloading a file that was shared with you (not owned by you), it is often slower. Google prioritizes the owner’s original requests. If 100 people are downloading the same shared ZIP file, your connection joins a queue.
Even with a 1 Gbps fiber connection, Google Drive rarely exceeds 400 Mbps for a single file download. This is due to TCP congestion control, per-connection limits, and Google’s own fairness algorithms. google drive file download speed test