Hey Eric,
You use parenthesis to group your calculations, so in your case it would go like this:
( thisComp.layer(“Rotating Lens Part”).transform.zRotation+88.7 ) * .81
and just to further explain it, if you wanted to the divide that result by 2+2 you would do it like this:
( ( thisComp.layer(“Rotating Lens Part”).transform.zRotation+88.7 ) * .81 ) / (2+2)
Hope that makes sense.. also there’s a forum for expressions.. you should find the link on the menu at the top of this page.
-Lloyd
https://aescripts.com