I cannot imagine simply throwing out (to landfill) every item that ceases to function perfectly.
Mending is definitely a skill worth nurturing. Some mending jobs are relatively simple while others are a bit more complex. Replacing a trouser zip definitely falls into the latter category in my opinion. It is not one of my favourite tasks. However, there is enormous satisfaction at restoring an otherwise useless garment to a functional piece.
The first step is to carefully remove the existing zip. Replacing a zip is made more difficult by the fact that it is not the final step when the garment was originally constructed. Unpick as much stitching as required to insert the new zip.
One side pinned in place.
I stitched the first side and worked out how to place and stitch the other side.
Here is the final result with the fly folded back to show the zip. It was a previously salvaged zip from a worn-out garment and I was fortunate to find a reasonable colour match and the correct length.
And the zip works.
Looking perfect and ready to wear.