A bombshell new forecast from Zillow finds more than one in three American housing markets heading into decline over the next year — and the cities taking the hardest hits are the ones that seemed untouchable just four years ago. Of the 894 housing markets Zillow tracks, prices are expected to fall in 309, hold flat in just 14 and rise in 572 through March 2027.  Nationally, Zillow now projects home prices will go nowhere over that stretch — a sharp downgrade from last month’s prediction of a 0.5% gain.  The flat national number is the least important part. What matters is what’s happening underneath it. America’s housing market is fracturing along geographic lines, with Zillow forecasting price declines in 309 of the 894 metro areas it tracks through March 2027 — a sharp downgrade from last month’s prediction of modest gains.…