There is a clear route up Cupid and Grizzly from Loveland Pass so no need to repeat that in detail, but it's worth talking about how to get to the summit of Black Mountain from Grizzly.

The route is hard to find (even worse in snow) and requires a short bit of Class 4. Maybe someone would argue it's "stiff Class 3", but even in summer it took some technical moves and had a fair chance of a slide of doom. I wouldn't take anyone up this way that isn't comfortable with 15 or 20 vertical feet of easy technical moves.

The route starts with the Class 1 trail over Cupid to Grizzly Peak. Proceed to summit Grizzly Peak.

From the summit of Grizzly Peak, head west toward Black Mountain. You can see it clearly, but navigating the rocks is going to take a little routefinding. Also, there is no reasonable bail-out option past here - you have to come back the way you came and re-climb Grizzly or you're facing a LOT of scree leading to chutes to nowhere. So, assess the weather and especially the wind - it can get channeled over this ridge with enough strength to be dangerous.

Stay slightly to the right (north) of the ridgeline approaching the first sub-peak, and you'll find a goat trail that descends the north side to the first dirt saddle.

The first dirt saddle is plenty wide, so no serious concern about exposure yet, but it's going to get a little harder to move quickly. Might want to assess the weather at this point. You won't be able to move fast after this, and routefinding is non-trivial. If you get off-route, it goes to Class 5 immediately.

Cross the dirt saddle to the right of the second sub-peak, but then you'll find things get steep before the third sub-peak. Right between sub-peaks two and three, turn left for a few feet and downclimb Class 3 just a few feet so you can see this next photo - the crux of the route.

You can take the dirt ramps in the bottom center of this photo to the dark stone and find a Class 4 chimney. The rock is mostly stable (though a couple of holds came loose, so check 'em). I climb 5.9 and 5.10 in the gym, just to calibrate my comments for you. Conditions were ideal, but I still felt compelled to focus while climbing this in hiking shoes and a backpack. Downclimbing it later on the way back took substantial focus thanks to high-altitude hypoxia, and if there was ice, this would warrant some gear.

I still recommend the chimney as the easiest way. The light-green rock on the left is very shifty scree, and on the right, it's Class 5.

After the chimney, not a big deal... stay on level as you cross the second dirt saddle and then turn left in front of the serious rock. A nice three-foot-wide walkway wraps around the left side of the rocks, not super-obvious until you're close to it but very convenient. Beyond is the usual summit shale.

You just scramble up that last hundred feet to the ridge on your right, and find the summit... but before you do, you might want to turn around and make a mental note of the exact location of that little three-foot-wide walkway that got you here, because it is totally not visible on the way back until you are right on top of it, and if you don't find it, now you have Class 5 downclimb problems.

Remember, you really do have to go back over this terrain, including downclimbing that chimney. There's no easier way - don't let the chutes tempt you. And back on Grizzly, you really do have to re-climb it or face a ton of side-hilling on questionable scree.