YOU SAID:

The most difficult thing to master is mastery

INTO JAPANESE

習得するのが最も難しいのは熟練です

BACK INTO ENGLISH

The most difficult thing to master is skill.

INTO JAPANESE

習得するのが最も難しいのは技能です。

BACK INTO ENGLISH

Skill is the hardest thing to master.

INTO JAPANESE

スキルはマスターするのが最も難しいことです。

BACK INTO ENGLISH

Skill is the most difficult thing to master.

INTO JAPANESE

スキルは習得するのが最も難しいものです。

BACK INTO ENGLISH

Skill is the most difficult thing to master.