Check out this video, specifically about zip maintenance: https://www.youtube.com/watch?v=66MmbXcT2tg&list=PLDlmJ3J-_OLKYAcpMXpA4zgnqCTDfk8LJ&index=4
If you can't watch the video for whatever reason, essentially follow these steps:
1: Regularly inspect zips and pick out large pieces of debris with a toothpick.
2: Close zips then cover zips in soapy water and open zips.
3: Brush out any remaining debris from the zip teeth with an old toothbrush.
4: Close all zips.
5: Wash as per the wash instructions provided.
6: Once dry, roll the zip out like so and run a soft lead pencil along the internal edges.
7: Finally, open and close the zip a few times to ensure it runs smoothly.
