It’s widely accepted that zombies make a constant, distinctive moaning sound which would make it difficult for them to attack using the element of surprise (see: The Nature of Zombie Verbalization), but even if they don’t make any noise at all, the smell of rotting flesh would be enough to announce their presence at a great distance.
No scent is more distinctive, or revolting than death. A tiny dead mouse under the stairs, or behind a wall is enough to putrefy an entire small home. Zombies occupy dead, decaying human bodies, so imagine that stink multiplied by 100, or even 1,000!
As a general rule, zombies would be smelled well before they’re ever seen. As they approached, their stench would become so overwhelming that it could easily cause humans in the vicinity to become physically ill.
So the idea that a zombie could hide behind a tree, wall, or door without being detected is extremely unlikely. The possible exception is a freshly reanimated zombie. But the rot smell would begin as soon as six hours after death, and depending on the time of reanimation, this leaves a very small “stealth” window.
This notion also brings up an important question related to the zombie hunting style: can they sniff out prey? Even if they are physically able to access a sense of smell, it could be argued that because of their own strong odor zombies can’t smell anything. Which means that they would not use this sense when tracking humans.