Why Does Rosetta Stone Use 打开 With 拉链?
我要打开外套的拉链 is fine.  打开 has the sense of &quot;open&quot;.  &quot;I want to open the zipper of my jacket&quot; is a good interpretation.
拉开(unzip) also works. E. g.  拉开拉链; 把拉链拉开;etc.