Hello!
I might be a bit late to the party but thought I could still contribute. I'm a UK national (so non EU) getting married to my EU fiancé in Switzerland this summer (EU nationality but born and raised in Switzerland, so basically Swiss haha). We've had the joy of going through all the paperwork so I can give you a brief breakdown and hope that your paperwork will take less time than me!
1. Get in contact with the Swiss embassy in Belgium (info will also be available online) and gather all the documents required to prepare your application. If you live in Belgium you will have to apply for the marriage in Belgium first through the embassy. You might need some documents to be certified and apostilled so you need to factor in the time.
-I started the procedure in the UK in March this year and was able to get all my documents certified and had an appointment with the Swiss embassy in London end of April
2. In the meantime get your fiancée to get in touch with her local registry office in Zurich (each town has an allocated local civil office). They will need several documents from her so she can request that in the meantime as well whilst you are sorting your side of things in Belgium
-Likely to take 3-4 weeks if some ID documents need to be reissued
3. Once you get an appointment and complete the application process at the Swiss Embassy they will need to send all the documents to the cantonal office and then to your local registry. They might want to do further ID checks or check that your wedding is not a sham (I would say this would unlikely be the case in you situation)
-Overall this will likely take 4-6 weeks from the day of your appointment at the Swiss embassy
4. Once the cantonal authorities and the local office receive your dossier they will process it and get in touch with your fiancée so she can provide her documents. They might contact you again at this point to clarify a few things if required. If all is ok then they will allow you to go ahead and book a preliminary appointment with them.
5. You will then have to book an appointment with the local office to decide on civil marriage formalities and sign paperwork. You and your wife will have to be present in person for this. Once this is done you can decide on a date for your civil wedding (need to be within 3 months of that appointment date)
6. On the civil wedding day you will receive a marriage certificate and yo can use it along with your other ID documents to apply for a B permit. (Have a look at the regulations in the canton you intend to reside in). As a EU citizen I suspect you could potentially apply for a B permit without the need for a marriage certificate if you already have a job offer lined up, but check the legal guidelines online. As an EU citizen you also won't need a visa to enter CH so that's one less thing to worry about, but as always check the links that the others have provided it will give you all the info you need! If you're married you will probably get a B permit and not an L permit, you should then be treated like any other Swiss or EU citizen already in possession of a work permit who is looking for a job so if you have a good CV and cover letter you'll stand a good chance!
The longest waiting period will be when the Swiss Embassy in Belgium will send your documents to the relevant Swiss canton and local registry office for processing and checking, this takes about 4-6 weeks.
However please note that depending on the canton, the waiting period to get married can be quite long ! I've heard that in cantons like Geneva and Vaud people are waiting up to 4-5 months before being able to choose a date. It wasn't the case for me and my fiancé, our local office is a very small one and they had lots of free dates, so I would ask you fiancée to check with her local office, they will be able to give you an estimate of the waiting time.
Unless it's significantly easier to get married in Belgium, I would advise to just get married in Switzerland if you're planning on moving there anyway because otherwise you probably will need to get your Belgian marriage certificate recognised in Switzerland that that's gonna take even more time and add to the cost! It does cost a bit to get married: expect to spend at least 300-400 CHF per person for just the admin fees (ordering ID documents, getting them certified, embassy paperwork fees, local civil registry fees)
My experience has been fairly smooth so far, even as a non-EU resident (thanks to Brexit). I started the procedure in March, had my appointment with the embassy end of April, heard from the canton May-early June and now we have our appointment and civil wedding date both booked for mid August. I will be moving to CH early next month to prepare! I'm also moving to CH without a job at the moment, but if have proof of funds and proof of your relationship with your fiancé in some shape or form this should be no problem.
Always tell the truth to the Swiss authorities and abide by the local rules.
It's a lengthy process but you'll get there! Any questions feel free to ask, and congratulations!!