From ZCWiki

This page describes the different file types that you can create and use with Zelda Classic.

Quest Files

.qst - Quest File 

These files contain games "quests". To play, see loading a custom quest. To edit, open ZQuest and choose File/Open. You may be asked for a password.

.qsu - Unencoded Quest File 

Like .qst, but you will never need a psssword to open or edit these. Use File/Export/Unencoded Quest in ZQuest to save.

Import/Export Files

These can be used only in ZQuest via the File/Import and File/Export menus.

Map (.map) 

A single map. On importing, you can choose one of these options:

Total Copy 

Use this option if you want to erase the original map you are importing to. With the next 2 options, blank screens are not imported.

Prefer Original 

If the map you are importing has non-blank screens where the original does, the original screens will be used and the conflicting screen will not be imported.

Prefer Import 

Like the above except that conflicting screens on the import map will be imported, erasing those screens on the original map.

Dmaps (.dmp) 

Dmap settings.

Tiles (.til) 

A tileset, the til file contains the actual tiles and the palette file their colors. (When importing tiles and combos you can specify which page of your current tile or combo sheet to start the import on, so that you can avoid erasing current tiles and combos.)

Subscreen (.sub) 

Custom subscreens.

Palettes (.zpl) 

Colour palettes for tiles.

String table (.zqs) 

Strings.

Combo table (.cmb) 

Combos. These are the actual combos, not the tiles.

Graphics Pack (.zgp) 

Combos, tiles and palettes all in one.

Quest Template (.zqt) 

Compressed version of graphics pack.

Unencoded Quest (.qsu) 

A full quest file, but not compressed like normal .qst files.

Key Files

.key 

Key file for a quest. Create by ticking the "save key file" checkbox when you set a quest password. If a valid keyfile is in the same directory as your quest, then

In ZC, you have automatic access to the level 4 cheats.

In ZQ, you do not need to enter your password.

Key files are meant for quest developers and perhaps testers, you do not as a rule supply these to players.