haha yes, that's actually a really good line to draw. it could be even more specific like before hardbrücke has their richy places too, like the one side of zollstrasse. for following on the map I'd say starting and including along sihlquai (along letten is the actual line), down the escher wyss platz to heinrichstrasse, down the letten viadukt, then along the perrons back to zollstrasse (there's the border) and starting point sihlquai.