I would like to do a few instructional videos

I don't have Photoshop on my Mac. From what I have seen of displays of it's interface, the elements seem to be generically fairly small. You might try making a test Photoshop screen recording at full screen and then uploading it to You Tube to see whether it displays satisfactorily.

What you could try is to make a full screen view recording of your instructional video, showing the mouse clicks to activate the various Photoshop features. Then import the screen recording video into iMovie. You could then split parts of it as necessary and use the Ken Burns feature of iMovie to zoom in on specific parts, such as the Photoshop interface elements. You would just make the Ken Burns start and end rectangles identical size.

So, for example, you have the unzoomed image:

And then zoom in on the controls:

You need to experiment a bit. You might actually be able to create the zooms while making the screen recording, by pausing and switching to drag select to select a portion of the screen to record, that would effectively zoom in on the smaller selected portion. You could piece everything together in iMovie.

-- Rich

You could also take screen shots of the Photoshop controls, crop and zoom them, and mix them in with your video clips.

Or split your video into separate clips and use the Ken Burns effect on the clips to zoom in an out as the video runs.

-- Rich