The Zombie Stockbroker is, as the name suggests, the reanimated corpse of a stockbroker. They have only two attacks; firing their shotgun, and kicking the player if he/she gets too close. The shotgun has a fairly tight spread, which makes it powerful even at long range.
The best way to deal with a Zombie Stockbroker is to stay far away from it. A blast from its shotgun at short range can inflict major damage, especially on higher difficulties.
However, being far away from the Stockbroker still doesn't mean it can't hurt you. Even at long range, one or two pellets will manage to hit the player. This can be very dangerous with groups of Stockbrokers, as they can quickly chip off the player's health, especially on higher difficulty levels.
When paired with other enemies, Zombie Stockbrokers are a high-priority threat, especially at low health as their bullets cannot typically be avoided.
The rocket launcher works best against them. One rocket will kill it and the Stockbroker will make no attempt at dodging it.
Groups of Stockbrokers can be taken out with either the Uzi or the rocket launcher. With the uzi, the player needs to make sure cover is nearby so the player can pop in and out of it so that they don't get hit by multiple shotgun blasts, and with the rocket launcher, the player should fire a rocket at a target, then immediately switch to another target and fire while the first rocket is still in the air.
The shotgun used by Zombie Stockbrokers can be seen used by the bodyguards escorting Serious Sam during the cutscene after beating the Castle of Rock.
Stockbrokers seem to have been Italian, as when spotting and/or addressing Sam, they'll shout "Bastardo!" o"Maledetto!" or "Sei mio!" ("Bastard!", "Curse you!", "You're mine!"). When you kill them, you might hear them screaming "mamma mia!".