To point out, a simple shopping cart could be a fairly useful defense against zombies if the conditions are right: -An empty one (at least in my experience) isn’t to heavy, and you would be able to just swing it around in front of you with one hand and the other hand just has a simple pointy stick or something.
-In the event that the shopping cart was laden with many heavy things inside, you could possibly dump them out onto the zombie and knock it over so you can stab it repeatedly.
-Duct tape and/or rope holding together a massive row of shopping carts filled with rocks and other heavy objects could act as a simple, albeit useful, fence around your house, since they’ll hold each other together and not easily fall down, but still help slow down zombies.
-Grab a shopping cart, put heavy and pointy objects in it, roll it down the hill to see the chaos. 
-Move the shopping cart away as they lunge for it and they fall into a strategically placed spike pit
-While it’d be risky simply due to the chance of you falling off, you could probably get some speed, get on top of the shopping cart (like on the gif at the top), grab your machinegun and fire away!
-Of course, while the zombie tries to shove the shopping cart out of the way, you slam it right into its gut and down to the floor! Then kill WITH FIRE! 
-In short, this is the apocalypse, in times like these you need to make everything a weapon or defense, even just a simple shopping cart. All you need to do is figure out how 
You see, while I understand, it is in no way ‘needed’ to change how shopping carts function. I’ve never actually used the shopping cart tactic(s) that brought up this conversation, and even if it doesn’t change, I’ll probably never use it still.
-For me, I don’t really care what happens, I just want to point out the truth.
