Their suppliers’ business with them is found to have been sa

翻译：发现他们的供应商同他们的生意很令人满意.
（do）business with:同...做生意
be found to do:被发现在做某事.在这里直译就是被发现很令人满意,意译就是发现...令人满意.
主语是business；谓语是is(found to have been satisfactory);with them在这里修饰business,做后置定语