I saw there were tons of topics about these two concepts in the forum. However, there is one thing that unfortunately is still not clear to me.
Can we use Z spread to value a callable, putable, or anything that has an embedded option attached to the bond? I thought we could because Z spread contains the option feature, but apparently, we should use OAS which I don’t get why as OAS is the value of the bond without option, so I thought the Z spread was appropriate. However, as I was doing one question, I totally messed up.