Don't shoot off your mouth. If you think there is a better way, say so lah.
Anyway, have been going to Zoo for donkey years. Favorite way back is via Upper Thomson road. Would rather miss the overpriced Khek run Yong Tau Fools. The earlier threads is about what is the least convoluted way to get back to South Bound SLE.
As for GPS navigation, looks like you are in a dinosaur era if you are not prepared to learn new technology. Nokia, Googlemaps, Apple are all into satellite navigation. Its one of the essential kit for a keen backpacker.