I took a second look at that schematic and noticed it only had one knob and a slide switch like this 1978 EHX Silencer on Reverb (
https://reverb.com/p/electro-harmonix-the-silencer-1978) instead of three nobs and send/return jacks like the new Silencer in the review link. If you want a comparison to late 1970s tech, check out this DOD 230 clone vid:
. It's an optical noise gate, so it works a little different than original Silencer, but you get the gist... I don't think 1970s tech will do what you want it to do after someone reverse engineers it for us.
If you want to see the new EHX Silencer pitted against the Zuul, check out this video:
.
TBH - I can't tell much difference between the two in that vid.
Since the Decimator and Zuul run on 21st Century tech, I think this is a better way to go than trying to reverse engineer that late '70s schematic, and I can't really tell the difference between them in this vid:
. Since you can get a PCB of the Zuul (as the Muzzle) @PedalPCB this might be the path of least resistance and easiest way to resolve your issues. The P-Dip version of the THAT chip was obsoleted around the time I bought the classic version of the PCB. I was lucky to find one. It looks like the SMD version of the 4301 is hard to find now, too. THAT has a newer SMD-only chip (4305) that PedalPCB has available as a retrofit module for the classic Muzzle. This vid by Ola England is what influenced me to buy the classic muzzle: