The problem with a circular saw is that it would cut as the blade is coming up and this tends to splinter the "plywood" that you are cutting. A plywood blade will help. I do a fair amount of woodworking in my shop and the only way I will cut plywood is an a tabelsaw since I can control the splintering of the wood. I only rough cut plywood with a skill type saw.
If you only have a couple of cuts talk to a cabinet shop.