Slick tyres for Bianchi Zurigo CX bike

+1 for Schwalbe Durano. I put some on my commuter the other day and what a difference it's made to the ride quality. They roll so nicely compared to the Conti gatorskins I have on my other bike. Whether they make a difference in terms of protection, we'll see - but I'd be happy to stick with them on any future bikes.

I'd go for at least 28mm - Schwalbe Durano, Bontrager Race Lite Hardcase or Vittoria Rubino Pro III.

Conti GP 4 Season are very popular but not cheap. Schwalbe Marathon Supreme also not cheap, though they are more robust and would last a lot longer. 32mm or wider will give nicer ride.

I'd be willing to bet that the 30mm in that specification refers to the depth of the rim, not its internal width. You need to find the width - look for a very small number on a sticker that looks something like ETRTO 622x19, 622x23 etc.

For the record my Boardman CX has 23mm wide rims and I ran 23mm Vittoria Rubino Pro 3 tyres on it at 110psi for a while with no trouble other than a hard ride. On 25mm Rubino Pro Tech (at 100psi), it's transformed and just flies.

Conventional wisdom is to make sure your tyre is 5-6mm or in old money a 1/4" bigger than the rim.

Don't do what Cannondale did with the first Bad Boy back in the noughties, they put 25mm rims with 25mm tyres which lead to a lot of dented rims.

There are loadsof 35mm tyres to choose from, the question is what do you want from the tyre?