Podejście jest niemal tak trudne jak zejście.

Because both podejście and zejście are neuter singular nouns, and the adjective has to agree with the noun.

• to podejście → neuter singular
• to zejście → neuter singular
• so: trudne = neuter singular form of trudny (difficult)

Compare:

• trudny problem — masculine
• trudna droga — feminine
• trudne podejście — neuter

In this sentence, trudne agrees with podejście.

Tak ... jak means as ... as.

So:

• tak trudne jak = as difficult as

The full comparison is:

• Podejście jest tak trudne jak zejście.
  = The ascent is as difficult as the descent.

With niemal, it becomes:

• Podejście jest niemal tak trudne jak zejście.
  = The ascent is almost as difficult as the descent.

This is a very common Polish comparison pattern:

• tak duży jak — as big as
• tak szybki jak — as fast as
• tak interesujące jak — as interesting as

Niemal means almost or nearly.

Here it modifies the comparison:

• niemal tak trudne jak = almost as difficult as

Its placement is natural before tak, because it is really qualifying the whole as ... as phrase.

You may also hear prawie instead of niemal:

• Podejście jest prawie tak trudne jak zejście.

Both mean roughly the same thing.
Niemal can sound a little more formal or literary than prawie, but both are common.

In normal standard Polish, when you say that something is something or is a certain way, you usually use jest.

So:

• Podejście jest trudne. — The ascent is difficult.
• Zejście jest łatwe. — The descent is easy.

Unlike some languages where the present-tense to be can be dropped, Polish normally keeps jest in ordinary sentences like this.

You may sometimes see omitted copulas in:

• headlines,
• notes,
• very informal shorthand,
• poetic style,

but for a learner, the safe rule is: use jest here.

In this sentence, that is the most likely meaning: ascent/climb up and descent/way down, especially in a hiking or mountain context.

But both words can have other meanings in other contexts.

Podejście

It can mean:

• ascent / climb up
• approach (method, attitude, way of dealing with something)

For example:

• Mam inne podejście do nauki. — I have a different approach to learning.

Zejście

It can mean:

• descent / going down
• exit / way down / coming off something, depending on context

So yes, in this sentence they are best understood as the ascent and the descent, but these nouns are not limited to that meaning.

Yes. They are nouns formed from verbs.

• podejść — to go up to / to approach / to climb up
• zejść — to go down / come down / descend

From these, Polish forms the nouns:

• podejście
• zejście

These are often called verbal nouns or deverbal nouns, though in practice you can just think of them as normal nouns derived from actions.

That is why they often refer to the action or result of going up/down.

No change is needed here, because jak in this comparison works like as in English.

The structure is:

• X jest tak trudne jak Y.
• X is as difficult as Y.

Both podejście and zejście are in the nominative form here.

So:

• podejście — nominative
• zejście — nominative

That is normal after this kind of comparison.

Not in this sentence.

Use:

• tak ... jak = as ... as
• bardziej/mniej ... niż = more/less ... than

So:

• Podejście jest tak trudne jak zejście.
  = The ascent is as difficult as the descent.

But if you want more difficult than, you would say:

• Podejście jest trudniejsze niż zejście.
  = The ascent is more difficult than the descent.

So jak is correct with tak, and niż is correct with comparative forms like trudniejszy.

The given word order is the most neutral and natural:

• Podejście jest niemal tak trudne jak zejście.

Polish word order is fairly flexible, so other orders are possible for emphasis, for example:

• Podejście jest tak trudne jak zejście.
• Niemal tak trudne jak zejście jest podejście.
  (much more marked, used for emphasis or style)

For everyday use, stick with the original order. It sounds natural and clear.

A rough pronunciation guide:

• podejście ≈ po-DEYSH-cheh
• zejście ≈ ZEYSH-cheh

A few key points:

• j in Polish sounds like English y in yes
• ś is a soft sh-like sound
• cie in this kind of ending sounds roughly like cheh with a softer start
• ej sounds a bit like ey in they

So:

• po-dej-ście
• zej-ście

The exact sounds are more subtle than English spelling can show, but that approximation is good enough to start.

It is basically neutral standard Polish.

The only slightly elevated feature is niemal, which can sound a little more formal than prawie, but it is still completely normal.

So these versions are both fine:

• Podejście jest niemal tak trudne jak zejście.
• Podejście jest prawie tak trudne jak zejście.

The first may sound a bit more polished; the second a bit more everyday.

Grammatically yes, but context strongly suggests ascent.

Without context, podejście could mean:

• approach in the abstract sense
• climb/ascent in a physical sense

But because it is being compared to zejście (descent), the physical movement meaning is much more likely.

So a learner should read this as something like:

• The climb up is almost as difficult as the climb down.

That pairing makes the intended meaning clear.