Zemlja writes the consonant z and takes the numeral nine. Its name is the Slavonic word for earth or land, one of the plainest nouns in the whole set of letter names, and it belongs to the run of names that can still be read as ordinary words rather than as labels whose sense has been lost.
The letter records a voiced sibilant, and it sits immediately after the sign for the affricate dz in the Glagolitic order. That neighbouring is not accidental. The two sounds were distinct in the earliest Slavonic and merged in most of the later languages, so the pair of letters together is one of the places where an early manuscript shows a distinction that a later copy has levelled. When a scribe writes z where an older exemplar had the affricate, the merger has already happened in his speech.
In the numeral system the letter is the figure nine, reached by counting the Glagolitic letters in their own order from the beginning. The value is written in the ordinary way, with the letter set off by points and covered by a stroke, and nine is common enough in chapter and verse numbering that it appears frequently in that form in the gospel manuscripts that make up most of the surviving early corpus.
The sound has been stable and the letter has passed into every Slavic orthography that descends from the Slavonic tradition.