The Zero is a great looking and flying plane. After making several modifications, it is a very fine plane. Having said that, here are the problems.
1. The plane requires 2 pounds of weight in the nose if you use the OS-160 as the instructions recommend. In fact the plane was built for this engine. Since that is the case, the manufacture should have known it would take 2 pounds to balance and should have taken that into account when building. The plane flies graet with this engine.
2. The retracts are the pits. They are so bad that when turning on a paved surface the planes wing tips will almost touch the ground due to sway in the retracts. I replaced with Robarts air. Decide what retract you will be using before cutting the hole in the top of the wing.
3. The retract hold down plates are poor grade ply and are glued in using hot glue. They must be replaced with aircraft ply and epoxy.
4. The contraption that is supposed to be used on the elevator is unbelievable and was throwen away. Use carbon fibre rods from 2 servos mounted as close to the front as possible.
5. Throw away all hardware except the tank. It is phillips head and metric.
6. The pilot looks like he has been eating persimmons for 6 months. Replace with a Japanese pilot from Hanger 9.
7. The cockpit can be improved by adding leather to the pilot head rest and arm rests.
Be sure and use the groments that come with the canopy or you will be replacing it. How do I know that?
The cowling is installed in a way that other should copy. A great design that helps you align it.
The plane can be bought for less than $500.00 at your LHS.
Hope this helps