Zone is relevant to 35mm in that it engages you with the light.

I don't own a spotmeter, rarely use the meters I do have, and none of my cameras have auto-exposure. Despite that I'd recommend learning the principles of zone to anyone, even if they (apparantly) never use them.

If you THINK about shadow placement, about contrast, and about highlights then it can only be a good thing.

If you can look a working print, and your brain has the vocabulary to consider the relative tones within it, then you're on the way to improving it.

Even without a meter, without running loads of tests, even if you never "do" any of the things your supposed to, the vocabulary of zone, and the experience of learning it is of great assistance.