Zcash will top $800 as Grayscale's May 12 spot ZEC ETF filing and the July Ironwood migration collide to lift demand. Traders will point to ZEC trading around $517.13 after a 6.7% 24 hour jump and a torrid 1,300% gain over the past year, while Ironwood moved more than 500,000 ZEC into a new shielde…