As stated above, you have a very nice frame set. I have a 2001 Lemond Tourmalet and a 2002 Poprad, I love riding both of them. The Tourmalet, I believe has about the same geometry as the Zurich, but I am not sure about any difference in the forks. My Tourmalet with the stock unicrown, steel fork fits 28mm, all brands I have tried, with no problem. I switched from threaded to threadless set up with a carbon fiber fork, it still fits the 28 mm I have tried on it, but the clearance is barely enough, maybe not enough for some. The Poprad is a CX bike, ergo, very different geometry and clearance. I actually ride the Poprad more due to being able to fit up to true 33mm tires. Knowing how much space you have to work with is definitely a help in deciding on tires, but brands very substantially in width. Also, with some forks, it is the fork crown or brake caliper that is the limiting factor, not the fork legs. The wheels are another factor in actual tire width. Unfortunately, without input from someone that has tried the specific tire, wheel, bike set up, it is a bit of guessing and trial and error.
Building a bike for the first time is a challenge, especially if you are as mechanically challenged as I am. It can be more costly than one anticipates, in particularly if one is set on specific items. It can also be frustrating at times. However, for me. when I finish a bike and all is operating as it should, the bike looks good and close to what I had pictured; it is high in satisfaction, feeling of accomplishment, and the real reward is a fine riding bike that you put together.