I'm trying to change an image added at the end and drag the end points so it's longer. I have to zoom in, I finally get there, then it suddenly zooms back out again. It's so annoying that I keep losing the scale that I worked so hard to get to.

Absolutely!!! Bring back the zoom in and zoom out with the scroll wheel. If some people prefer hot keys, make that a customisable setting.

Adding a key hold doesn't make a feature more friendly from an accessibility standpoint!

Furthermore, the behavior is inconsistent - if I hover over the transcription and use the trackpad / mouse-wheel, I will scroll up-down whether I am working in the transcript or not. If I am hovering over the timeline and I use the trackpad, it will scroll left-right, but not in-out?

The behavior in Storyboard while holding Command is exactly correct; adding a key modifier is an unnecessary hurdle. Please restore the Classic functionality here - or at the very least, provide an option in a Settings menu somewhere to enable it!

I've been told by Zac that this is for "accessibility" and they refuse to bring it back.

WHAT?

Scrolling without CMD does nothing, so in no way is this blocking any accessibility features. Not to mention, many other editing apps use the scroll wheel for zoom, preserving good UX, while still having accessibility options.

I smell a BS excuse for poor planning and bad UX choices.

you can press control + scroll wheel, but why require two hands?