If you can save after the planet puzzle that you did successfully, that's what I would do. Then you can work on the next section.
I believe the walkthrough explains the zodiac puzzle well:
With the test sheets open in the diary, work on the right column set of test on the right page.
The object of the puzzle is to match the symbols to the name of the zodiac.
The sun icon at the bottom scrolls the name of the zodiac.
The 2 crescent moons icon moves the bottom zodiac one to up position.
Study the sequence of the names of the zodiac and see which one is out of order. The symbols are in order.
The correct sequence is: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces.
Check from top down which one is the next sign that is not in correct position below Aries.
Use the sun icon to move the next misplaced zodiac to the bottom-lowest position. The next one that is off is Taurus.
Use the 2 moons to flip the position of Taurus to be one up. Lower it the bottom position again using the sun icon and then one up again. Do this until Taurus is below Aries.
Then work on Gemini. Continue on until they are arranged in order.
The correct zodiac name is lighter in color than the rest.
Once correctly done, the puzzle can not be moved anymore.