Indochinese peninsula vs Indochina

Indochinese peninsula and Indochina both are nouns.

Word	Noun	Adjective	Verb	Adverb
Indochinese peninsula	Yes	No	No	No
Indochina	Yes	No	No	No

As nouns, Indochinese peninsula and Indochina are synonyms defined as:

Indochinese peninsula and Indochina: a peninsula of southeastern Asia that includes Myanmar and Cambodia and Laos and Malaysia and Thailand and Vietnam

Indochinese peninsula (noun)	Indochina (noun)
a peninsula of southeastern Asia that includes Myanmar and Cambodia and Laos and Malaysia and Thailand and Vietnam	a peninsula of southeastern Asia that includes Myanmar and Cambodia and Laos and Malaysia and Thailand and Vietnam