ᐅ Installing a concrete screed: Subfloor preparation

I am planning to install a concrete screed in my basement, where there used to be oil tanks. I have now switched to district heating. There is a depression of about 40mm (1.5 inches) where the tanks were. The original concrete floor and masonry are coated with a kind of rubber paint to prevent oil from soaking into the masonry in case of leaks.

Can I leave this coating on, or should I remove it?

I suspect it will be very stubborn to remove. What is going to be applied over it later?