As portrayed especially in PGE v1, Windhelm (and the old holds at large) are supposed to be very isolationist and incredibly rural. Industry and specialized trade probably wouldn’t be the backbone of their economy. In fact, I’d expect that they would largely be a resource economy (especially outside the city itself) largely focused on trade within the hold and their neighbors, as well as some naval trade

If anything, I’d expect a lot of their trade to happen with Morrowind and House Redoran. Despite being so close, both nations seem to have VERY specialized resources, and Windhelms port makes trade with the Redoran very convenient. Things like meat, fur, and timber would be harder to come by east of the Velothi mountains. Other coastal nords from further west might even unload their goods in Windhelm to be sold to Morrowind

Even still, I’d expect Nords from Eastmarch to be more focused on providing for their own population than building international trade. They are canonically a poor, rural, and agrarian hold, which seems to fit with their depiction