Madrid is 6 hours behind Beijing
Best overlap: 2:00 PM to 6:00 PM in Beijing is 8:00 AM to 12:00 PM in Madrid.
For a call that suits both sides, look at 2:00 PM to 6:00 PM in Beijing / 8:00 AM to 12:00 PM in Madrid. Around 4 hours of overlap is enough to work comfortably, as long as meetings don't drift to the end of one team's day. Because Madrid and Beijing don't both observe daylight saving, plan to re-check the overlap around March and November.