One major problem of the BTZS is you really need a densitometer, but in reality its only taking the Zone System and expanding on it, which seems to make a lot of sense if your producing prints by alternative processes.
Pyrocat-HD is a superb developer and once you've settled on your dev times and effective EI it's usually very easy to use a different film and as Sandy King says be in the ball park, then tweak it to suit yourself.
My own tests with Pyrocat-HD were made with Tmax100, but Tmax400, Fortepan 400 and EFKE PL25 are just as easy to use, however the Fomapan 100 & 200 films are quite different. They really do need testing afresh, the ball-park times etc don't quite seem to work, the results are extremely contrasty. I have 30+ rolls of 120 and a few boxes of 5x4 and 9x12 so I jhave to get it right. When I had to use FP4 & HP5 recently, two films I've not used for 20 years (the only 120 B&W films available in Chile), it was quite the opposite my ballpark dev time 15mins 1+1+100 @ 20°C worked perfectly.
I'm adding that numerous posters on APUG state that their EI's for Foma films are 2 stops below the box speed, my guess is my own test will indicate something similar.
My notes show that I got good results by rating 35mm Foma 100 at an effective film speed of 50 and semi-stand developing for 14 minutes with Pyrocat-HD 1+1+100 @ 20°C.