Solid Hardwood, Engineered and Laminate Flooring - removing water damaged subfloor

We were planning a bathroom remodel which involved removal of all fixtures and laying vinyl over the existing floor. When we removed the vanity, we found significant water damage and a leaky water supply line. We've repaired the water supply and are planning to remove the subfloor and replace it, but are having a very difficult time removing it. Are there any tips to removing this? There seem to be 2 layers of very stubborn plywood. Also, any other tips for potential pitfalls we can avoid?

My experience has been to set the depth of the blade of a circular saw to cut through the top layer of flooring and use a pry bar or crow bar or hammer claw to pry it off.Only the nails should be holding it.
Hopefully only the area under the vanity is ruined, and only the top layer.
If after getting the top layer off you find damage to the sub flooring it is best to go back to the nearest floor joist.
You can nail a sister joist to the existing one to give you something to build your new floor from.
Replace either 1 or 2 layers of plywood and you are almost good as new.
You may need to use a floor patching compound to smooth out the patch before installing vinyl floor covering. Follow directions on the package.