XF 1.3 Compound Xen If Statements

I'm trying to build an if statement for guests, the first post and not in some forums.

I have the first post, and guests with this if statement
<xen:if is="{$post.position} == 0 AND {$visitor.user_id}">

xen:if is="!in_array({$thread.node_id}, array(y, z))"

You can't overload with additional if statements.

should I do an if statement inside an if statement?
That wouldn't normally be a good thing to do.