This is one of the different forms of the Hebrew letter Zayin that also has different spellings.
What is interesting about this Hebrew letter is the shape resembles a CROSS and has the numerical value of seven, 7.
The Hebrew alphabet existed during the time of Moses and long before the Cross of Calvary.
Hebrew and Greek use letters and NOT numbers to represent numerical values with Zayin being the seventh, 7th letter in the Hebrew alphabet.
The numerical value of Zayin is 7 with 7 being the NUMBER OF REST also called THE SABBATH meaning REST as God rested on the 7th day.
Hebrews chapters 1-5 tell us that our REST, SABBATH is in the completed work of Jesus Christ.
SO, even the Hebrew alphabet becomes PROPHECY concerning the Messiah of Israel.
Hebrews chapter 4:
1–Therefore, let us fear lest, while a promise remains of entering HIS REST, any one of you should seem to have come SHORT OF IT.
Probably meaning some have heard (verse 2) but not acted on the promise of the Gospel. The door will be open until their death or the Church Rapture.
2–For indeed we have had GOOD NEWS PREACHED TO US, just as they also; but the word they heard did not profit them, because it was not united by faith in those who heard.
3–For we who have believed ENTER THAT REST, just as He has said, “AS I SWORE IN MY WRATH, THEY (verse 2) SHALL NOT ENTER MY REST,” although His works were finished from the foundation of the world.
4–For He has thus said somewhere (no chapter and verse at the time of this writing) concerning the seventh day, “AND GOD RESTED ON THE SEVENTH DAY FROM ALL HIS WORKS”;
5–and again in this passage, “THEY SHALL NOT ENTER MY REST.”
6–Since therefore it remains for SOME TO ENTER IT, and those who formerly had good news preached to them failed to enter BECAUSE OF DISOBEDIENCE, Acts 17:30.
7–He again fixes a certain day, “Today,” saying through David after so long a time just as has been said before, “TODAY IF YOU HEAR HIS VOICE, DO NOT HARDEN YOUR HEARTS.”
8–For if Joshua had given them rest, He would not have spoken of another day after that.
9–There remains therefore a SABBATH REST for the people of God.
10–For the one who has entered His rest has himself also rested from his works, as God did from His.
11–Let us therefore be diligent to enter that rest, lest anyone fall through following the same example of disobedience.
12–For the word of God is living and active and sharper than any two-edged sword, and piercing as far as the division of soul and spirit, of both joints and marrow, and able to judge the thoughts and intentions of the heart.
13–And there is no creature hidden from His sight, but all things are open and laid bare to the eyes of Him with whom we have to do.
14–SINCE THEN WE HAVE A GREAT HIGH PRIEST WHO HAS PASSED THROUGH THE HEAVENS, JESUS THE SON OF GOD, LET US HOLD FAST OUR CONFESSION.
15–For we do not have a high priest who cannot sympathize with our weaknesses, but One who has been tempted in all things as we are, yet without sin.
16–LET US THEREFORE DRAW NEAR WITH CONFIDENCE TO THE THRONE OF GRACE, THAT WE MAY RECEIVE MERCY AND MAY FIND GRACE TO HELP IN TIME OF NEED, 1John 1:9.