Please don't omit the context and the full sentence. So is this the full sentence you are asking about?
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Then it means "Among , is the hardest". is a compound that refers to the three basic necessities in our life ( = clothing, = eating, = sheltering/housing/housekeeping).
refers to the same thing as here. Since is a short on-reading which makes little sense in isolation, this person rephrased it as , which is a wago that means the same thing.
But what this (= ) actually translates to depends on the context. It may refer to buying a new physical house, or it may refer to housekeeping jobs such as cleaning. The sentence may just mean "I like cooking but cleaning my house is a hard task to me".