Delta's MU partner page says:
"Accrual is not eligible for the following MU-marketed flight ranges: MU6001-6199, MU6501-6599 and MU6701-6799"
Is your flight in any of those ranges?
"Eligible Flights: Accrual valid on flights marketed by China Eastern or Shanghai Airlines, operated by China Eastern, Shanghai Airlines or other SkyTeam Partner."
CZ is a member of SkyTeam, so you're good there.
If you'd bought a CZ-marketed ticket,
this would apply instead.