I had the enclosure on my last boat.
It was as Randy described on the windows, screens on the outside, clear in the middle, privacy canvas on the inside. The screens were sewn into the canvas cover, the rest were sewn fast at the top, with velcro around the edges to keep it all shut. there were tieing strings between each layer to secure them when rolled up. I'm pretty sure the screens were sandwiched between two layers of canvas.
The zippers zip from top to bottom, so gravity keeps them closed. They also zip from bow to stern so they don't work loose underway, or when towing. I marked mine with a magic marker, but you could sew in landmarks so you know quickly which piece goes where and what is top and bottom. That comes in handy on windy days during installation. I've had big plastic zippers, and smaller metal zippers, big plastic are lots easier to use.
2006 Forester 19 Fish (new deck and carpet, Pontoonstuff interior, 2019)
1996 Mercury 50 ELPT4S
1983 Sea Nymph FM171 Striper (complete rebuild from hull up, 2014)
1985 Johnson 70 J70ELCO
Raystown Country, PA