What shrubs are you considering?

In zone 6, you are limited as the extent of broadleaved evergreens hardy for your area and not too many coniferous or needled evergreens are happy in shade. Taxus (yews), various species of vaccinium, a few hollies (Ilex) and rhododendrons will work, but some may become very leggy or sparse and produce few flowers in heavy shade. Borderline hardy for your area are laurels and aucuba - both are extremely shade tolerant. Leucothoe is another choice, also likely marginally hardy. Specific microclimates may increase your selection. Have you visited local nurseries, garden centers or even arboreta to see what's available for your area in the way of shade loving shrubs?

I grow Leucothea in Z5 as well as Kalmia latifolia and Pieris floribunda. Rhododendrons offer a wide choice. I have Ilex opaca growing in shade.

Cold-suited camellias