zusammensetzen
to assemble
To make or put together a whole from individual parts or components.
Nach dem Umzug mussten wir alle Möbel wieder zusammensetzen.
After the move, we had to assemble all the furniture again.

to assemble / be composed / meet
Loading your saved state.
to assemble
To make or put together a whole from individual parts or components.
Nach dem Umzug mussten wir alle Möbel wieder zusammensetzen.
After the move, we had to assemble all the furniture again.

'Zusammensetzen' (to assemble / be composed / meet) is a separable verb. The prefix 'zusammen-' comes at the end in a main clause, while in a subordinate clause and in the infinitive it remains attached to the verb.
Er setzt das Modellflugzeug zusammen.
He assembles the model airplane.
The verb consists of the adverb 'zusammen' (together) and the verb 'setzen' (to set/put). The literal meaning, 'to bring something together into one place,' helps you understand the different meanings.
Die Kinder setzen die Bausteine zu einem Turm zusammen.
The children assemble the building blocks into a tower.
This verb has both non-reflexive and reflexive meanings. When you assemble something, it is non-reflexive ('etwas zusammensetzen' = to assemble something). When something consists of parts or a group meets, it is used reflexively ('sich zusammensetzen' = to be composed / to meet).
Ich setze gerade den neuen Stuhl zusammen.
I am assembling the new chair right now.
In the meaning 'bestehen aus' (to consist of), the verb is always reflexive and used with the preposition 'aus' followed by the dative: 'sich zusammensetzen aus etwas' (to be composed of something).
Wasser setzt sich aus Wasserstoff und Sauerstoff zusammen.
Water is composed of hydrogen and oxygen.
When 'sich zusammensetzen' is used without the preposition 'aus,' it means that a group of people meets to discuss something or work together.
Die Familie setzte sich am Abend zusammen, um über den Urlaub zu sprechen.
The family met in the evening to talk about the vacation.
to form / educate
'bilden' and 'zusammensetzen' can both mean that several parts become a whole. 'zusammensetzen' fits especially well when you take concrete individual parts and build or assemble something from them. 'bilden' is more general: parts can make up a whole even without someone actively assembling them. For example, you say that several people form a group. When the process of building is important, 'zusammensetzen' sounds more precise.

Vor dem Termin setzt Paul den neuen Bürostuhl zu Hause zusammen.
Before the appointment, Paul assembles the new office chair at home.
Fünf Schülerinnen bilden zusammen ein neues Team für das Projekt.
Five schoolgirls form a new team together for the project.