whats the difference in length? Not sure if this would work, but if you take both sets of axles to a shop that specializes in axles, you could have them mate the two...

lol now this is where my mechanical grammar gets funky as i don't know what the 2 parts of the axle are called, but basically take the part that fits into the hub from the protege, and mate it to the part that goes into the tranny from the mx3

We've done it before when putting in the lsd tranny from the lantis. just reversed we used the mx3s to fit the hub.