You have definatley left alot of time but you might have problems as it is very competitive in Zurich finding somewhere, especially close to Zurich HB.
There are the obvious ways of looking which are www.comparis.ch
which are both decent websites and can obviously be accessed from anywhere. When I first moved to Zurich, I found that they tend to do mass viewings on properties. I went to one viewing and there must have been 30 people looking around at the same time!!
I think you are going to need to visit the properties to properly get one and when you do visit, take your work contract and Permit to show them everything at the viewing and hopefully you will be able to complete the letting application form when you are there. Thats what I did.
I found that englishforums.ch was excellent and that is how I found my flat which is just outside Zurich in Feldmeilen. Everyone on here is really helpful and there are always flats being posted on here, but as with anything be quick!
For deposits if you are not wanting to put a deposit down they run Swiss Caution where bascially you pay a few hundred francs every 6 months and they put your deposit up for you. Might be a help if upfront monies are tight.
Anyway hope you find somewhere and coming out in July will be fantastic. That is when I came to Zurich and the lake is brilliant at that time of the year!