I have combination of Czech, Hindi and Urdu in my book:
http://icebearsoft.euweb.cz/bharat.php
The book is written in Czech but contains words and sometimes even
sentences in Hindi and Urdu. The lines are often broken within the
Urdu text. Since the book contains more than 300 pictures, almost all
paragraphs require \parshape. The book was typeset in XeLaTeX using
polyglossia. I had a lecture on typesetting this book (in Czech), you
can see the abstract of the lecture in Czech and English and see the
slides (in Czech only) here:
http://icebearsoft.euweb.cz/lectures/floatingtext.php
I wanted to show how the line should properly be broken, in one of the
slides I do it in one \item inside the itemize environtment. You can
see that it works well. At least, in the Urdu-Hindi Dictionary
published in India the lines are broken the very same way. Thus
XeLaTeX allowed me to do whatever I needed.
This does not make much problems because your main direction is LTR and you just insert few RTL things. The real challenge starts when your document is mainly RTL.
-------------------------------------------------- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex
