RCFREEK,
First the engine you have selected is very good and will fit the Zen just perfectly; however, OS engines need a 5% nitro minimum, 10% better.
The prop you have selected seams to small for this engine, try to use 11X7 or 10X8.
CG as you described is far too forward, Try to do the following:
Check the wing angle of attack relative to the fuselage and stabilizer. (It has to be +1 deg) if it bigger than that adjust the fuselage "opening" for the wing
Move the battery as far as possible towards the tail. (You may need an extension)
Same goes for the receiver.
Check if it possible to move the engine backwards on the engine mount (you may need to drill a new holes)