Simple multiplying can be done with Visual Cortex alone. Also have Esnho’s Triple Multiplier.
To get the screen, you basically just have to invert the signals first (like with Syntonie or Fox’s quad inverters), then run it through a multiplier, then invert the result of that. That’s where the patching can get complicated.
Honestly, since I don’t have a way to get two full color image signals into my system at present, I haven’t found the need/desire to do this too much yet. But have played around with patching this up a bit to see the possibilities. And, like I said, anticipate more need once TBC2 arrives.
I don’t know if it is at all practical (or indeed even all that useful, beyond inasmuch as more outputs always seems somewhat useful) to have access to both Multiply and Screen outputs simultaneously on the 8hp version above. Maybe it is just a switch to have one or the other? I dunno. Spitballin’ here!