To disable the zoom on the collection page, you'll need to open style.css.liquid in your assets folder. Look for and remove this code:

#content .main_box .box_1 img {
  -moz-transition: all 0.3s;
  -webkit-transition: all 0.3s;
  -o-transition: all 0.3s;
}
#content .main_box:hover img {
  -moz-transform: scale(1.2);
  -webkit-transform: scale(1.2);
  transform: scale(1.2);
}

It should be somewhere around line 1270 depending on your version of the theme.