How to remove stuck clear pipe off flowmax macerator

If this is a Valterra elbow or similar, I would try pouring hot water over it to make the plastic expand. If you can spray PB blaster into the inside of it at the same time onto the macerator piece only to shrink it, that may help too.

A rubber strap oil filter removal tool might work.

It may not be as tight as you think. I frequently have trouble undoing our EZ-Coupler sewer hose because there is such a tight tolerance. It requires a firm grip and twist to let go.