I can't speak on those glow plugs, never heard of them.
Th ZD-11's have been discontinued at Autozones. Some stores still have some on hand, and if they do the price will show up as $.01. Yes a penny. Read more about that
HERE.
As far as your hard start goes, I don't think 2 bad glow plugs would cause an extremely hard starting situation? I could be wrong, but we'll keep this bumped up for you till a tech comes along.
Are you plugging it in?
Does it help?
Good Luck