str.replace is the wrong function for what you want to do (apart from it being used incorrectly). You want to replace any character of a set with a space, not the whole set with a single space (the latter is what replace does). You can use translate like this:
removeSpecialChars = z.translate ({ord(c): " " for c in "!@#$%^&*()[]{};:,./<>?\|`~-=_+"})
This creates a mapping which maps every character in your list of special characters to a space, then calls translate() on the string, replacing every single character in the set of special characters with a space.