Η ζάντα είναι ίσια.

No. In Modern Greek, Η is the capital form of η, and here it is pronounced ee.

So at the start of this sentence, Η is not an h sound. It is the feminine singular definite article, meaning the.

It tells you that ζάντα is being treated as a feminine singular noun and that it is definite.

In other words, η ζάντα means the rim.

It also shows that ζάντα is the subject of the sentence, so this is the nominative form.

A very good habit in Greek is to learn nouns together with their article:

• η ζάντα not just
• ζάντα

That helps you remember gender much more easily.

In this sentence, yes, ζάντα is feminine, and the ending -α fits that pattern.

Many Greek nouns ending in -α are feminine, but not all noun gender can be guessed perfectly from the ending alone. That is why learners are usually encouraged to memorize the noun with its article:

• η ζάντα

So the safest clue is not just the ending, but the full phrase η ζάντα.

Είναι is the present-tense form of είμαι, which means to be.

Here it means is.

A useful thing to know is that είναι is used for both:

• he/she/it is
• they are

So Greek relies on the subject and context to make the meaning clear.

In this sentence, since the subject is singular (η ζάντα), είναι means is.

Because Greek adjectives must agree with the noun they describe.

Since ζάντα is feminine singular, the adjective also has to be feminine singular:

• masculine: ίσιος
• feminine: ίσια
• neuter: ίσιο

So:

• ο δρόμος είναι ίσιος = masculine
• η ζάντα είναι ίσια = feminine
• το ξύλο είναι ίσιο = neuter

Even though ίσια comes after είναι, it still agrees with the subject.

Here ίσια means something like straight, true, or not bent/warped.

With a wheel rim, the idea is not usually that it is a straight line in a geometric sense, but that it is not crooked, bent, or damaged.

So in this context, ίσια is a very natural descriptive adjective.

A simple English-friendly pronunciation is:

ee ZAN-da EE-ne EE-sya

A few details:

• Η = ee
• ζ sounds like z
• ζάντα is roughly ZAN-da
• είναι is roughly EE-ne
• ίσια is roughly EE-sya

The stress falls on:

• ΖΑΝ-τα
• ΕΙ-ναι
• Ι-σια

The accent marks show which syllable is stressed.

So:

• ζάντα → stress on ζΑΝ
• είναι → stress on ΕΙ
• ίσια → stress on Ι

In Modern Greek, written accents are important and are normally included.

The article η does not get an accent here because it is a short one-syllable function word.

Yes, Greek word order is more flexible than English word order.

The sentence as written,

• Η ζάντα είναι ίσια. is the most neutral and straightforward order.

But Greek can move things around for emphasis. For example:

• Ίσια είναι η ζάντα.

That sounds more marked, like emphasizing straight or contrasting the rim with something else.

For a learner, the original order is the safest and most natural one to use first.

In normal Greek, you would usually keep the article and say:

• Η ζάντα είναι ίσια.

Leaving out the article would sound unnatural in most ordinary situations.

Greek uses the definite article more often than English does with specific nouns, so when you mean a particular rim, η is expected.

No. Greek normally does not need an explicit subject pronoun here.

You do not say something like:

• Αυτή η ζάντα είναι ίσια
  unless you specifically want to emphasize this rim or contrast it with another one.

The basic sentence is perfectly complete as:

• Η ζάντα είναι ίσια.

That is very normal Greek.