These fast zombies are a pain for fresh spawns because they see you kilometers away and the follow you for ages, and of course the can easily catch up
Zombies could be able to track you for about 200-400 meters and after that they should "forget" that they were chasing someone, but should continue walking in the same direction
It would be cool to avoid hordes of zombies
(and it would be nice if zombies had loot)
Also add crawling zombies (broken legs, without one leg/both legs,...), zombies wihout both arms/both arms broken (no damage), with one arm (less damage than a normal zombie),...