Zoom In when Replying to Mail

I'm getting older and there are times when I'm checking/replying to mail on my laptop (MacBook Air), and I need to zoom in to read. For messages that I have received, this is no problem: Command +. Works like a champ every time. The problem I'm having is on replying to emails. Command + doesn't work. The only Zoom option that comes up from help increases the size of the email, so it zooms across the screen.

Is there anyway to zoom in for replies, and also I imagine, forwarding? It seems really strange that it works so easily when reading and email, but doesn't register, or show as a menu option, when replying.

Thanks very much