Why "flat is better than nested"?

[Lawrence D'Oliveiro]

In message
<d4e7f8b9-9526-4bf5-b4d7-e398912eb638 at b19g2000prj.googlegroups.com>, rustom 
wrote:

> If you take zen seriously you dont get it
> If you dont take zen seriously you dont get it
> That -- seriously -- is zen

I don’t get it.