Could someone please confirm for me that Thursday is in fact NOT a public holiday in Zurich.
My movers have just called me asking to change the moving date as they think it's a public holiday which I think it is not.

Cheers

It is not a public holiday.

You can point your movers to Feiertage.ch – There's no letter in the field for Fronleichnahm (Corpus Christi) and "ZH". But if the company is based in another canton, they may be closed then.

Frohleichnam (Fete-Dieu /Corpus Domini/Corpus Christi) is observed mostly by Catholics and is a public holiday in the following cantons: AG, AI, FR, JU, LU, NW, OW, SO, SZ, UR, VS and ZG. If your relocation company is located in any one of these cantons, it would probably be closed.

And Ticino as well.