JLPT N1
～ならいざしらず
if it were ~, that'd be one thing, but; ~ might be understandable, but
Structure / Usage
Noun + ならいざしらず / Verb (plain) + ならいざしらず
Example Sentences
子供ならいざしらず、大人がこんなことをするとは。
If it were a child, that'd be one thing, but for an adult to do this...
一回ならいざしらず、何度も同じミスを繰り返すのは問題だ。
Once might be understandable, but repeating the same mistake over and over is a problem.