If you actually just want to use these pages as one-pager / landing-pages (as the url 'landing' suggests) it could also be done by adjusting your domain settings for abcd.com and efgh.com.
At least with my webhost I can adjust where a domain would look for its content. Setting the 'home' path to /landing/abcd (or actually seting the 'A-entry' of the dns registry accordingly) would do the trick on the server I'm working on – at least when all three domains share the same webspace.
So you might also consider asking your question over at stackoverflow.com or webmasters.stackexchange.com since it could be a more technical question.
