Yes and no. City district provides both - housing and jobs. Zones modify what job district provides. But if you have no zones then city district by itself provides no jobs.City Districts provide housing, Zones provide some jobs of a certain type or types
That's my main issue, you can't balance housing at all and you can't balance mixed outputs from 2 different zones since they both get their number of jobs from city district level. This rigid link is the most strange design decision to me. Leaving 3 most boring base resources as separate districts (that are not even being used when you have 100% urban planet) and putting every other resource generation into singular city district.
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