Complex sentence: The memo stated that Tamraz should be denied access to high-level government officials because his presentation was deemed by Heslin to be incomplete and he was believed to have a loose affiliation with Abu Nidal.
Split into simpler sentences: The memo stated that Tamraz should be denied access to high-level government officials. Both on the grounds of the frivolousness of his presentation (which was deemed by Heslin to be incomplete) and his loose affiliation to Abu Nidal.