🚀 go-pugleaf

If you take the sidehead approach that Niels suggest, you could do
this, but it would be a bit of maintenance.

Have your "xxxxx" flow content sit in text frames within anchored
frames. The anchored frames are then in a special conditionalized
paragraph ("z") in the *sidehead* before every "yyyy" flow section,
e.g.

z
xxxxxxxxxx yyyyyyyyy
xxxxxxxxxx yyyyyyyyy
xxxxxxxxxx yyyyyyyyy
                yyyyyyyyy
                yyyyyyyyy
z
xxxxxxxxxx
xxxxxxxxxx
xxxxxxxxxx
z
xxxxxxxxxx yyyyyyyyy
xxxxxxxxxx yyyyyyyyy 

The "z" paragraph is just a container for the anchored frames and
should contain no text.

When you hide the "z" tags, all of the "x" flow content will then
disappear as well. You'll have to manually customize the height of
each anchored frame/text frame pair though.

To adjust the spacings between the "y" flow to match at the bottom of
the anchored frames for the "x" flows, use the sidehead paratag ("Z")
and create space above overrides in this paragraph only to adjust the
vertical spacing to keep the x and y sections in sync. This way, you
have overrides confined to only one paratag.

To make maintenance easier, it might be worth creating a FrameScript
that would adjust the height of the anchored/text frame combo based
upon the amount of content in the instructor flow and then apply the
space above override to the anchoring paratag (z).