Want to replace plexiglass window in plastic coop with mesh, but how??

[BoundlessLove]

Not sure what mesh you have, but I definitely recommend using hardware cloth.

 

[RoseHawke]

Cutting plexiglass without cracking it is not easy. That's why I suggested finding a thin wood product. A thin metal might work too.

I think metal would work better, but it would still need to be secured to the coop. Any thin material a raccoon is just going to break or rip up and as you've pointed out, plexiglass will crack. A raccoon would just speed it on its way.

The most secure way, not necessarily the easiest, would be to build a frame to exactly fit the space, fasten the hardware cloth to that, then screw through the coop from the outside to fasten it in place using washers to keep the screws from crushing the plastic. You could probably skip putting screws through the roof although a couple wouldn't hurt.

 

[NanaK]

Cutting plexiglass without cracking it is not easy.

Actually it is not that difficult. If I can do it anyone can if they have the right tools.

You need a stable surface to work on. Use masking tape along the area to be cut. Use a fine toothed blade. Go slowly.
There are many sites that give good instructions just search "how to cut plexiglass".