Complex sentence: Another failure is that al-Ahmed's faction, which is based in Syria, does not have exclusive Syrian support and, considering that it is based in Syria, the party is susceptible to Syrian interference in its affairs.
Split into simpler sentences: Another failure is that al-Ahmed's faction, which is based in Syria, does not have exclusive Syrian support. Another problem is that, seeing that it is based in Syria, the party is susceptible to Syrian interference in its affairs.