We claim the ornamental design for a zipper pull, as shown and described.
FIG. 1 is a front perspective view of a zipper pull;
FIG. 2 is a back bottom perspective view of the zipper pull;
FIG. 3 is a top plan view thereof;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a left elevational view thereof;
FIG. 6 is a back elevational view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a right elevational view thereof.
The broken lines shown in the drawings of the zipper pull are for the purpose of illustrating portions of the article and form no part of the claimed design.