The following video demonstrates each syllable of the pinyin structure
and the exercise of pinyin/zhuyin with basic Chinese 4-tune pronunciation

Mandarin pinyin tunes
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to link more related multi-character Chinese words!

zēn, zén, zěn, zèn

third tune

zěn

how; what 怎 zěn

What should I do? How should we do? 怎麼辦 zěn me bàn
what; how 怎麼 zěn me	do; handle 辦 bàn