Critique my winter running workout

It's a nice workout. However, without knowing what else you are doing and your running history, it's not really possible to say whether this will be good for you. If all you're doing is this workout and a long run (you didn't define what long run is), then it may have very limited benefits.

Thanks Don.  I have completed two triathlon seasons but have been running for around 5 years but not long distances (nothing much longer than a half marathon).  I am not looking to gain a lot of speed in the first couple of off season months, but would prefer not to lose a lot of fitness.  I am focusing hard on swimming and am limiting my run frequency to twice per week.  My long runs rarely extend past 9 miles and are typically run at a pace of ~7:30 - 7:45.

For now, I would pick the workout you posted over intervals.

Any particular reason why?  Just curious.

Couple reasons.

A) I don't like intervals.
B) In my mind, intervals 4x4 at a real high intensity (which I am assuming zone 5 qualifies as), are used sparingly, and as prep for a specific race, not done year-round.
C) The set you described would still not be done every week, at least I wouldn't do it that way. I'd do long run, medium effort run, and a whole lot of easy runs. The "off" season (namely, the season you aren't in race-specific training) is about getting out the door as much as possible.

I would actually be more likely to do the workout you described, but slow down the paces and remove the recovery. Then it's a nice progression run.

Looks like fun.  A nice workout does not a training program make.   You don't say, but I'm going to assume this is your speed/interval workout and that you also have a couple of easy days and a long run day?  

Not a big fan of the uber-short distance at Maximum effort.  Prefer something that surges to max and eases back.  To many injurys from going as fast as possible until something breaks.  If you can't keep the pace up for a mile, then it's to fast for training.  Unless you're training for an event that lasts only 30 seconds. 

I like the pace based training for speed, better than HR zones.  Another alternative to the 4x 4' at Z5 would be someting like a 6 x 4' @6:30 pace with 2' jogs.   I'd suggest you find 3 different interval formats that you mix into your program.  Keep the body guessing, when to go fast and when to cruise.  Mix it up.

Last shot, you'll need to think bigger intervals when you step up from the10k to the HM.

so if, as you say, you are not looking to gain any speed, why do any VO2 stuff?
If you are going to pick between the 2 workouts you have in your OP I would go with the posted one.
If I was in your shoes I would go with doing the w/up and then doing a 5mi tempo/steady state at ~6:45 pace or maybe go the the 7/8mi distance you are already running and break it into thirds, 1st third easy, 2nd third moderate and 3rd third just below threshold (based on the numbers you have used in your post would be around 6:40-45 pace.)