comparatives - "Much more easy" versus "much easier"

My mom and I are having a dispute on much more easy versus much easier. For example, consider the sentence:

It's [much more easy]/[much easier] to do action X than action Y.

I say that much easier is correct and that much more easy is grammatically incorrect, while she says that both are okay. I understand that both are acceptable colloquially, but which is grammatically correct here? If you could explain why, that would be even better!