** ZTO Express (Cayman) 2057.HK falls 6.4% to HK$135.1, lowest since April 9
** Stock set for biggest one-day pct drop since April 7
** Chinese express delivery services group posts Q1 revenue of 10.89 bln yuan ($1.51 bln), a 9.4% y/y rise, vs analysts' forecast of 11.93 bln yuan
** Adjusted Q1 EPS of 2.44 yuan higher than year-ago 1.75 yuan/share; analysts had estimated EPS at 2.78 yuan
** YTD, stock falls 4.6%
($1 = 7.2130 Chinese yuan renminbi)
(Reporting by Donny Kwok)
((donny.kwok@thomsonreuters.com))