Pull a search for "windshield" here using the search tool at the top right (the most under use feature on this KB) and see what comes up?
That material though, with those deep of cracks, I high doubt you can buff those out and get them to come clear. All I could find on the subject below, and I would just replace it if you cannot see through it any longer.
https://www.hunker.com/13421655/how-to-get-plexiglas-clear-again