Hi Carl,
I've not previously read anything by Zenkevich, and I really enjoyed this one. Thanks for posting it. I think a lot of this is working pretty well.
A question. Do you need to exactly match the Russian metre, since after all you're translating? I do think you'd have a much easier time of it if you wrote this in IP. I'm assuming the metre is more natural/easier when written in Russian? Starting every line on a stressed syllable seems at times to push you into difficulties and more-awkward phrasings than if you'd been writing in IP. Not that I think I'll change your mind, of course

But I'm interested in why, and I'd also be interested to see this in IP (so maybe I should give it a go!). All that said, I quite like the sound of the metre. Terser and always pushing forward off the first stressed syllable.
From the crib, I first took the opening to be saying that N has nicotine in his lungs and fumes in his brain. Then the fog creeps in (I take this literally, not a mental fog, though possibly that's intended too). Then the "you" is addressed to the day: after the rain, it's now wrapped in fog -- since the rest of the poem can't easily be taken as self-address (which is how I'd first read the "you"). However, I guess it also could even be that "Fumes in the brain and nicotine in the lungs" is not referring to the N, but is instead (also?) figuratively describing the day.
Anyhow, I think it perhaps the translation is a little more confusing due to the inclusion of "creeping fog" in the initial list, since the nicotine and hazy brain (taken literally) are properties of humans, and creeping fog (taken literally) is a property of the day. But maybe you've grouped them this because you think first line is also addressed to the day? Or because the metre makes it hard to more closely echo the original. Still, in the original, the fog is separated out.
S1L3: "bapTIZED" is the only time you don't start a line with a stressed syllable. But presumably this is an acceptable substitution? Or do you say "BAPtized"?
S2L1 "let go" might be nicer sonically, than "release", I think, picking up the 'g' of gasp.
I guess you have "narrow apertures" because the metre prevents an easy way to have single aperture -- or an "outlet", for that matter, which has nice double meaning in English (and maybe in Russian too?). Still I'm thinking the idea/subtext is pressure, difficulty in release, and several narrow apertures still convey that, I think. And if the "outlet" in the poem relates to the sirens and foghorns (steam-driven?), as the translation seems to take it to be, the poem does then become plural with these.
S2L2 I wondered why the sirens wail, whereas in the crib they weep. Wailing is more conventionally associated with sirens, and absent the crib, the personification, and the connection to weeping (to weeping and wailing) is likely to be overlooked by the reader. Besides, "wail" rather duplicates "howl".
S3L2, there might be something more interesting/image-based than "generated". Something along the lines of "spewed/belched (up/out/forth)" might well fit with the chomping and slurping theme, if you can find a way to fit it in.
S4L1, "with a pang" strikes me as overly rhyme-driven. The line also seems closer to the original without it. That said, hard to see a rhyme for "pan". Could you work with "the soul grows anxious for a span", meaning "for a while"? The next line implies it's anxious for a period of time (before dark).
S4L3, again, plural rather than singular for the metre, but I don't think it detracts from the meaning. Would "specks" be an option? Suggesting perhaps an even smaller particle, and the 'p' picking up on "pan". I do like how you add a toilet reference with "pan" that (presumably?) isn't there in the original, but works really well in context.
Thanks for introducing me to this poet. I enjoyed reading your translation.
best,
Matt