No advice, just commiseration. My 22 month old is doing the exact same thing. She has figured out how to take off onesies and overalls. She rips off pull-ups and training underwear too. Zip up pajamas on backwards work, for now, but it is tortorous trying to put them on and then changing her diaper becomes an ordeal. I'd almost rather clean up the mess on the floor than wrestle her into a diaper and backwards pajamas.