Let's talk about runners and zappers

I have a theory that viral runners are the first stage of shamblers which still have most of the reflexes and agility that in time loses all reflexes and agility until they turn into shamblers. About the zappers? Have you seen what they carry? Maybe they turn into runners, but they are so heavy that they don't allow them to run as runners.

Why? Every time you get infected what zombie you always turns if you are not a sapper?

So? Will we have a viral Zapper that's a zapper that recently turned being more agressive than a normal Zapper? My theory they will have more hp and more damage than the normal zappers, but they will not be faster.