I have four Shih Tzu males. One of the males has already established his Top Dog position but the youngest one 1 yr. 10 mos. is constantly fighting with the big dog and they are hurting each other. We are desperate so we are thinking of neutering all four. I do not know what to do since some people say its a good idea and others say the sugery will affect their overall attitude.

What should I do? Will my youngest male calm down after a certain age without having to castrate him? Please help!

Castrating all your dogs will not help.If you want to go down that route then you should castrate the lower ranking male.I suugest you ask your vet about 'chemical' castration first...its a way of simulating castration through using medication.This way you can see how it works and its not permanent.
Archer

neutering will not stop the problem
you say 1 male has already already established top position what i would do if it was my dog i would leave his collar on in the house, if a fight started i would be there  grab his collar hold it at the back of his neck  and with a very firm "no" would  not let go until he submitted to me as pack leader .once this established the problem will go .   4 dogs you will get pack behaviour .i have 4 dogs myself my pack is settled now i had problems in the early days i had problem similar to you .i also believe in socialising dogs as much as possible.my 4 are not saints though
i like those little shi tzu there lovely dogs  i hope you will get your problem sorted out .

ps i forgot to mention i have found crate training to be very effective, i also forgot to ask what is causing the fight is it food or possesions when does your dog attack the other .