The ornamental design for a weightliftingassembly, as shown and described.
FIG. 1 is a top, front, right perspective view of a weightlifting assembly showing my new design;
FIG. 2 is a bottom, rear, right perspective view thereof;
FIG. 3 is a top angled view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a front view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a left side view thereof;
FIG. 8 is a top view thereof; and,
FIG. 9 is a bottom view thereof.
The broken lines immediately adjacent to the shaded area define the bounds of the claimed design and form no part thereof. The broken lines depicting the remainder of the weightlifting assembly show features that form no part of the claimed design.