This was brilliant!
So many clever little touches and those precious "aha!" moments.
I played through the normal (with-zero) version using Xournal++. I started by highlighting only the listed words, and after reaching page 0 I went back to puzzle 3 (as suggested), where I started to figure out the tricks before going through each puzzle again sequentially to find the hidden words. I hit a few little snags (ANIMAL / ZODIAC, grr...) but no major blockers.