There is a picture and article on Rhus lancea at Plantazafrica on the link down below. The term African Sumac is not much used here , you will see its common names listed at the top of the article in about 4 of our 11 official languages. At the site go to the Search section and enter Rhus lancea.
I have 2 of these in my garden and they are nice medium height shade trees , evergreen and not too dense so that other plants can grow underneath them quite easily. They are fairly fast growing , a nice green foliage with a dark brown stem . They need a full sun position . They should be watered until established and from then on can be left pretty much to rely on rain water but grow faster if watered about once a week during dry periods. They do not like too wet or soggy sites. They are not effected by the frost we get around here but I am not sure how they would withstand extreme frost and snow as we do not really have these conditions except in a handfull of isolated , sparsely populated areas.

Here is a link that might be useful: Plantzafrica