David,
As has already been said, it is all a matter of measurement. Take into account the size of your tooling, height of the toolpost mounting surface to centre height and compare with the dimensions for a given QCTP. For example, my lathe is a generic 9 x 20 Asian clone and I use a model 000 wedge-type from Uncle Ketan's Emporium. I'm very pleased with it. Have a google for videos on YouTube. There are several on there that explain the method of selecting the correct size.
Wedge-type QCTP Model 000
That page also has links to articles on fitting such a toolpost to either a mini lathe or a Myford, so I'm pretty sure that size would suit your Zyto.
I dare say you could get away with a larger one, but I don't see any benefit to be gained by doing so.
John