Hi Mike, I grew it in New Jersey zone 6 and here in North Georgia so I don't see why you couldn't grow it in between.
The snow in NJ. never seemed to bother it nor these soggy Ga winters so I say go ahead plant it.

Below is a website that lists four varieties of cotoneasters that are hardy to zone 4. I am sure that there are many other varieties so I would just check the specific varieties you might want to grow to see before planting. I have had several varieties that surivived zone 7a with no problems.

Here is a link that might be useful: hardy cotoneasters