Yes, there is a page zoom option, found in a menu that its icon looks like a rectangle and two lines below. There is a percentage initially at 100%. That is the page zoom.
I had a bookmarklet on iOS Safari that shows the source code of a page for a year or two and it runs fine. Been through iOS versions, and it still runs. If it doesn't run, blame that oddity on Apple devices where some bookmarklets are not registered as one but some are. I got that on macOS but unsure if that is the same on iOS.
If bookmarklets don't work, you can create a shortcut on Shortcuts that run JavaScript on a website to disable zoom.