I may be the odd ball here but I make small coin purses all the time with nylon zippers. The cool idea about nylon zippers is that you can customize it to the size of purse you are making by sewing over the nylon teeth.
So, if I am making a 6" coin purse and only have 9" zippers I just customize it to fit by sewing 'over' the teeth at the appropriate place and cut off the rest of it. If your needle is clunking, as someone else pointed out, it isn't seated correctly, tightened down and/or your needle is dull. I have sewn many little coin purses one right after another with the same needle. The needle isn't dulled by sewing over the teeth nor is my machine lagging because of it. I have watched many, many videos on zippered pouches and just as they do I sew over the teeth.