Yes, but the 34c is a "two piece" design, not three piece, and the handle is chrome-plated brass. On mine, only the top of the cap and the "base plate", which is soldered onto the handle, are zamak. Those parts should last a long time unless they get a very hard knock that compromises the chrome plating, so long as they are kept clean and dry. However, I agree the RR steel razors are a better value.
I replied with the "what" emote, because the question is hard to answer: It can be VERY random.I read something about zamak not being so nice as brass, and would like to know how long your merkur 34c's are lasting for daily shaves and how long did it last before it broke down.
Try getting a razor with a brass core or one of the cheaper stainless steel razors. Many often bash Parker, but I like their razors, but they are also quite prone to quality issues and also often nothing but zamac. Razorock razors are not that cheap anymore, but their Chinese copies are of very similar quality and often quite a bit cheaper. I would also like to mention Stando from Poland, his razors are excellent and still inexpensive.So I have replaced it but I will not buy another Merkur as the razor was well looked after and they seem not to want to warrant their products. I am buying a Parker instead.