HELP!

Question
Me and my wife are a four dog family, no children just four dogs.  We have a 10+ year non neutered male golden retriever, a 1 1/2 year old male neutered English bulldog, 8+ year old male neutered shih zu, and finally a 1 year old female, spayed imperial shih zu.  She had the golden and the male shih zu before we were together and had them since they were puppies.  We just added the bulldog and imperial shih zu about 1 1/2 years ago, and both were puppies that were introduced into our house and to the other two dogs.
 The problem we have just started a month or so ago.  Our bulldog, will unprovoked will just attack the golden without provocation.  The golden might be on the other side of the room, and the bulldog will rise and just attack.  The female imperial shih zu will protect the bulldog while the male shih zu will protect the golden retriever.  
 The bulldog, in most cases gets the injuries.  The injuries (numerous bites around the head area) don't even have time to completely heal due to the constant battles.  Again, this just started a month or so ago, and have no idea what to do.
 All the dogs, get equal amounts of attention, all sleep in our room at night.  The eat at different locations through out the house.  
 Our bulldog hasn't show aggression towards me or my wife.  We have began to put the bulldog into "time-out" by placing him in his crate when he attacks for about 30 minutes.  The bulldog and the imperial play without attacks, the imperial pretty much runs his show daily.
 The older male shih zu doesn't want anything to do with the bulldog or the other shih zu.
 Our older golden is going to die of stress related complications if we don't get this situation under some type of control.  The bulldog just continues these attacks DAILY ( 3-5 times a day)
 We check both dogs, and neither have any serious injuries.  All four are heading to the vet for shots and a check up next week.  Can you help with some type of guidance with the information I provided?

Answer
You need a certified applied animal behaviorist (NOT a dog trainer) NOW.  The Bulldog appears to be obtaining rank and your Golden is fast becoming an omega (dog which receives redirected aggression during times of stress or with inadequate human leadership).  NOT FAIR and not conscionable.  These dogs must be kept separated at all times until a professional has evaluated all temperaments in all dogs, carefully observed body language signals between the Golden and the Bulldog (and they ARE there, you just don't know it because most people don't, after all, "talk dog").  Your Bulldog most likely needs to be psychologically demoted under YOU (this would not be happening if you were actually in "charge") but this MUST be done after professional evaluation of the situation.  If you were to go ahead and enact behavior modification on your own, your situation could worsen drastically and very quickly.  Dog to dog aggression can be a predictor of dog to human aggression: proceed with caution.  Ultimately, your Bulldog may have to be re-homed; maintaining "rank" among a pack of dogs in the home is a timely and intricate procedure, requiring sophisticated awareness (which the behaviorist will hopefully provide you) and weeks, sometimes months, of ongoing work.

Because your Golden is intact, this may be part of the problem.  But this is an older dog who may not be a candidate for neutering and I DO NOT recommend you do this without a behaviorist's intervention, first.  Find such a professional at one of the following sites:
http://certifiedanimalbehaviorist.com/page6.html
http://www.arkanimals.com/ark/dg_expert_referrals.html
http://www.animalbehavior.org/ABSAppliedBehavior/caab-directory

Remember: the English Bulldog is NOT a casual companion, this breed requires a strong owner (but humane, positive reinforcement training only), extremely heavy socialization, and calm, consistent leadership.  Further, because of its recent popularity, it is a breed being turned out like hotcakes by money hungry idiots who care nothing for the temperament and genetic tendencies of their breeding stock.  This is not a casual problem, this is a serious issue causing all your dogs enormous stress (as you report) and which may cause the death of one (or more) of them, not to mention injury to human(s) who attempt to control or interfere with an attack.  Most veterinarians know a bit about behavior but most I've known have not had hands on, daily, experience with serious problems; however, a course of hormone treatment (progesterone) for the Bulldog MAY BE required if your behaviorist suggests it, and your veterinarian needs to be comfortable with this (or any other meds, STAY AWAY from Prozac and other SSRIs).  Go to the lists of behaviorists and fine one ASAP.