The Raspberry Zero is even more meager in term of CPU/RAM (it's still a first gen Broadcom CPU inside. It's not even ARMv7, but only ARMv6. It's single core CPU, with a very limited RAM - 512MB with no physical way to go beyond 1GB due to limited address pins). I should be okay-ish for a feature-phone (think the new Nokia 3310), given its spec (think the same, but with a crappier screen). But forget about running anything close to a "smartphone experience".