Recently I had to replace a 32" zipper in a leather jacket. This was a new experiecnce for me, so I thought I'd share what I learned. First of all ripping out the old zipper has to be done carefully so as not to rip the leather. And when you go to put the new zipper in you can't use pins to hold it. Pins would punch holes in the leather, which is something you don't want. I went searching online and found several helpful items. Use rubber cement to hold the pieces together. And then clamp it with office clips. Off to nearby Staples for supplies. First time I ever got sewing supplies at Staples!
Here's a shot with the rubber cement on the zipper before I put the pieces together
I'd paste a little and clamp it down.
When one side as all done, it was time to move to the sewing machine.
You want to set your needle tension lighter than you normally use, and your stitch length longer. I used 3 mm when my normal length setting is 2.2 mm. Check your sewing machine manual for the setting for your machine. Use one of the needles designed for sewing leather, and you want to go very slowly with your sewing
I used my machine's zipper foot and worked up to the clamp and removed it just prior to sewing that section. Here's a photo with the jacket all done.
Hope this has been useful information for you!