As has been stated; "making" a product and "manufacturing" a product while it may sound similar by the time that product sits on a retail shelf, the two are drastically different.
It would be one thing if a company has the where with all to manufacture all their own chemicals, mix those chemicals, source out their own (in house) design of packaging and finally bottle/package those products versus a company that buys chemicals in 55 gallon drums and simply bottles product based on formulas they have designed.
Both sell their product in a retail marketplace, although one may go for OTC while the other sticks strictly to web based sales. They BOTH "make" their own product.
Adams is one that I think of that's similar to a guy I once had as a vendor. He bought a franchise (similar to a tool truck type franchise) and sold a wide range of products. Lots of cleaning products (but some detailing stuff even back then). Don't know who makes their stuff, but it worked, and was cheap enough, and (MOST IMPORTANTLY) I had a guy that came to my office, wanted my business, and delivered it to my front door.
It wasn't ZEP (but I like their stuff), it was Castle, just checked and the company is still out there and looks to offer more than ever.