Irule rewrite

That is fairly simple to do - set the correct pool member and change the Host header.

But be clear that their browser will load the HTML from what it thinks is https://abc.com but it may have links to https://xyz.com embedded in the page, and if they click on a link then it may well take them to https://xyz.com/example.html instead of https://abc.com/example.html.

So it probably won't do exactly what you want it to do, unless the code on https://xyz.com is well written and doesn't reference the site.