The large horse rider monument located in Quanzhou, China here: Google Maps
Is this monument depicting Koxinga or someone else?
Can't find wiki articles or something in English.
Yes, yes it does. If you click layers on Google Maps, and the Wikipedia layer, you'll also get photos taken in the area. Several are from Panoramio, and are labelled "Zheng Cheng Gong" - see an example.
Koxinga (Lord of the Imperial Surname) is the customary Western spelling of the popular appellation of Zheng Chenggong,
So it would appear we've found our match :)
EDIT - UPDATE
If you then look at the Wikipedia page for Quanzhou, it informs us that:
Notable Modern cultural sites include: Da Ping Shan - The second tallest hill within the city limits, crowned with an enormous equestrian statue of Zheng Chenggong.
So that would seem to add confirmation to my findings.
EDIT - FURTHER FINDINGS
I've also found the following: