Learn Farsi: زندگی در شهر سخت است.

You absolutely could! Saying زندگی کردن در شهر سخت است literally means "Living in the city is hard" and uses the full long infinitive as the subject. However, زندگی is the root noun meaning "life" or "living." Persian speakers often drop the کردن to make the sentence shorter and more natural.

Why is there no "ezafe" (the linking sound) between زندگی and در شهر?

We use the ezafe to link a noun to an adjective or to its owner. But here, در شهر (in the city) is a prepositional phrase, not an adjective or a possessor. When a noun is followed by a preposition like در (in), you simply place them next to each other without an ezafe.

Could we change the word order and say در شهر زندگی سخت است?

Yes! Persian word order is quite flexible. Moving در شهر (in the city) to the beginning emphasizes the location, meaning "In the city, life is hard." Both versions are perfectly correct and natural, but the original sentence keeps "life in the city" together as the main subject.

Does سخت mean "hard" as in difficult, or "hard" as in physically solid?

It means both! Just like the English word "hard," سخت is used to describe situations that are difficult (like living in a busy city) as well as objects that are physically solid.