Frontier's "timber" wolf seems to share a bit of overlap in design with both Mackenzie/Northwestern wolves and Eurasian/common wolves (while also having its own inaccuracies to boot). Dr. José Castelló has some great references from his book
Canids of the World that I'll share here.
Northwestern wolves generally seem to be the leaner of the 2 subspecies, as even with their winter coat they're not very robust. Note the melanistic morph in the image, which I'm assuming isn't in PZ because it's a result in breeding with domestic dogs and not something originating from the wolf's genetics.
The common wolf here is far more robust, though its summer coat makes it look disproportionately skinnier than the summer coat. Eurasian wolves also have a brown/pseudo-erythristic morph not present as starkly in Mackenzie wolves. I do believe this is a variant present in PZ's wolves, however (though not to the same extent).
In anycase, the main grey-ish colour for both of these subspecies is extremely similar.