If your Zero is Dark Blue plastic & covered in rivets, it's the same one I built recently. It seems to date from the sixties, though it had an 80's copyright moulded into it. I built a Tamiya Zero at the same time and used the Tamiya to correct the Monogram. I added about 2mm in length at mid fuselage, and about the same to the tailfin. I built a cockpit and used a Tamiya canopy, which fits with a few fuselage mods, the Monogram one is hopelessly overthick.
People who keep knocking a certain British model company really ought to have a look at this kit (No names, we'll protect the innocent. And lawyers are not getting a penny out of me!!)
PS yes, I know the Tamiya is an M2 & the Monogram an M5, but the fuselage is the same (ish)
Pete