Unique rules when forming that grammar are highlighted like this.
Example sentences follow these rules too!
Joining and Nesting Markers:
Verb[た/る] - means that dictionary form and ta form are accepted.
Verb[causative[て]] - means て form of the causative form of the verb.
(A) いざ知らず (B) is a slightly old-fashioned expression, which nowadays is mostly used in writing. It literally means that “If it’s (A) then I don’t know, but for (B) ... ” where いざ (originally いさ) is an interjection similar to the modern さあ and indicates confusion about how to answer a question.
This expression is used to show the contrast between the extreme example (A) for which something might be the case, and then (B).
Often followed by expressions of surprise, impossibility, or criticism.