Guangzhou Toycenter Toy Firm is a maker (or distributor?) of handheld consoles, which uses the Digiking and Zhanglong brands.

The Digiking brand name may have originated with cloned Digimon keychains, but I have not conclusively confirmed those devices to be related to this company.

Manufactured consoles

Digiking ZL-720VT03
Subor SB-Z16AVT03