32-33 in waist. What size is best ?

Definitely a medium. I am a 32 waist and it fits good. Even if i was a 34 there would be room. Any bigger than a 34 i would probably suggest a large

Where is this manufactured and shipped from?

They are manufactured in CHINA so they are shipped from there. When I ordered off Amazon I got them once within 3 days and others within 5. Nowadays you get a date, then it changes. It may come sooner, or later.

Is there sizing information for these shorts and why is there an age range? What happens at age 46 that makes these not appropriate?

Not sure on the age thing. But the size chart is on the site. I have a 32” waist & 59 years old. I did large.

Do these shorts have a zipper anywhere? I noticed reviewers saying something about a zipper but I don’t see anything about a zipper in the description

Zipper, must not be the same shorts...the shorts I bought had not zipper. Draw strings and two pockets, although they are a little too short to my taste; as I wear them to the gym.