[markom]

I don't think that M92 can be quicker in that regard, but it's a lot better for other reasons like scribbling with exporting, multitasking, wi-fi, sd card slot etc.

Another option if endnotes and graphs were too small for our vision would be using magnifying glass or simply simultaneously using auxiliary tablet/eink for colors, scribbling, dictionaries (as I've been doing) or in your case quicker zooming and browsing.

I usually don't use 2-column mode for 2-column pdfs though (letters are too big for my liking that way and I can just see a quarter instead a half of the page), but I rather read it in landscape zoomed in without margins (fit-to-content-width in KPV kindlepdfviewer), like I would read any one-column A4/letter sized pdf there.
It takes about one and a half second for full screen refresh at flipping through pdf page (again four screens per page, back and forth, as at using 2-column portraite mode).

If zoomed without margins then the letters would even appear slightly bigger than on the A4 sheet of paper, so usually there is no need of zooming-in, but it's no problem to zoom-in by pressing alt+next/prev and then use joystick for panning (panning steps also adjustable).
Zoom level can be adjusted by shift+next/prev e.g. 16% or 32% and then by pressing alt+next/prev successively it goes up or down by 16% or 32% until desired magnification.

Of course DX is not as quick at flipping or at zooming as average tablet is, but I don't find it too slow for my needs (as some might do).

It takes about two seconds to enter 2-column mode that is usually good enough for magnification without a need for any further zooming and panning (if graph or text is not spread across two columns).

It takes about three seconds for zooming in 200-300%, about 2 seconds per screen for panning and second and a half to get back to fit-to-width landscape, fit-to-page portraite or 2-column view.
For quick jumping to other pages we can use go-to-page function, TOC, or numbers 1-10 for 0%, 10%, 20% ... 100% of the book.