We think it may be a gawk object. What I suggest you do is take all the ztds from the game leaving just the fences and animals. It will probably not crash at this point. Then add back a few ztds at a time. Do not save while doing this. Just add a few, run it to see if it crashes, exit out without saving, add a few more back.....repeat. If you can narrow it down I can then look at the various files.
I did notice you have Wild Wings ingame. Do not use this piece "WWscenery_finalfix.ztd Small aviary" That small aviary will crash your game as it has the gawk problem.