I saw the incident live as well as in many replays. I have more complaints for Martinez' initial behavior reagrding the hit batsmen and finger pointing than I do his response to Zimmer.
I am also younger and smaller than Zimmer. If I had been in that position I would have considered it a success to simply move slightly to the side and redirect Zimmer's energy past me. Zimmer's ukemi needs some work - especially if he plans to repeat the charge. Note that Martinez did not pursue Zimmer, he just avoided the majority of the energy.
For the record, I have been enjoying the playoffs but my team (Minnesota) is already finished. I'm not seriously rooting for any of the remaining teams.