The Hulk is an incredibly strong Rotinaj that can hit 50hp with its swing attack. It is large and red and moves at a fairly brisk speed. It takes a large amount of damage to kill and costs the Zombie Master 60 Resources to create.
BASIC: This is almost everybody's favorite type of zombie. They could resist a whole danmaku (curtain fire) without even realizing it. Basically, you will make use of these beasts in 3 situations: When a survivor is inside a room, whose only exit is a door. You will make 3-5 hulks get inside and thus sending the human player some nasty companions he/she will not be able to fight. In open zones without barrels nor molotovs. You will use then hulks as an assaulting team, leading crowds of shamblers behind or banshees to distract the survivors. Hulks are the only zombie type that can effectively be used in open ranged zones, as they have a lot of health points. Generally, every time you have plenty of resources and want to command an offensive against the humans. Hulks are mostly used as shields and not as tomahawks, mainly to protect the rest of the zombies, who are much more weak, forcing the survivors to kill the hulks first due to their high speed. Finally, I want to add something: Do not "spam" these guys, for two reasons: the first one, it's a lame tactic. Everyone will hate you if you do so, and you could even be kicked or banned from the server. And second, it's very expensive to do so.
ADVANCED: If you want to make the humans feel they're playing against the ultimate zombie master, you will always move and command the hulks manually. Letting them on their own is very uneffective due to the poor AI they got. So, that said, you will use the hulks in the situations exposed above, AND, you will select them after spawned ordering them to attack, block, or just move them.
If they're leading a group of other zombies, move them so the human bullets do hit the hulks instead of the zombies behind. Do not let the hulks alone, they're more powerfull when they're all together. Basically, use your imagination.
MASTER: There are two master hulk tactics. The first one is the one I call hulk volleyball. It consists in creating an ambush of two or four hulks behind a door, on its sides, so when a survivor comes in, the first hulk will hit and push the survivor to the second hulk, who will just finish him off. Here's a little diagram of how it works:
Hulk 1 <-----hit------> Hulk 2
The second one is forcing the survivors to move wherever you want to. This one is very hard to master and requires a huge control over hulks. You will move them manually, so the survivor's only way of escape is the one you want, forcing him/her to enter a room full of drifters or more hulks, for example.
Hulks will kill you if you get close. Try not to use meelee weapons, but you can use a Sledge Hammer as a last resort if need be.
Grab a rifle and aim for their upper body. 4-5 hits are usually enough to kill one of them.
Grab a shotgun and aim at their legs or upper body, trying to land all bullets in them. They're large enough and shouldn't be a problem at short range.
Grab a melee weapon, mainly the Sledge Hammer. This is a hugely scary tactic, but it works as a sledge can kill them with 2 hits from the hammer's secondary fire.
Run up to them, attack, then back up as soon as you hit.
If done right, the hulk will have taken damage, with you unscathed.
This does not work well though, as one hit with the hulk will take half your health away.
Aim for the head brother!
The head is their true weak spot. Not their legs.
if you can manage to hit their head, they will take massive damage.
It's incredibly difficult, and can usually only be pulled off with shotguns (and not very well either). Aim for the eyes of a hulk with a shotgun; you can usually hit their head this way at close range, but be careful of the hulk's swing.