How to make tools and armor unbreakable?

One way to do this is to use a procedure to replace the armor (while on body) with these commands:

1.14:
/replaceitem entity @p armor.<head,legs,ect> minecraft:<helmate,chestplate,ect>{Unbreakable:1b} 1
1.15:
/replaceitem entity @p armor.<head,legs,ect> minecraft:<helmate,chestplate,ect>{Unbreakable:1b} 1

Here is a good website for making commands:
https://mcstacker.net

I suggest using tags. MCreator allows you to create tags, even vanilla ones. Define a tag element, set it to minecraft, and make it the unbreakable tag. Then, put all the items you want to make unbreakable under it!

Set the durability to 0

which code block do i use for that?

Setting it's durability to zero made mine break instantly 

for armor, I have it be fully repaired every tick using procedures, for tools I make it so that whenever a block is broken or a mob is hit, it's fully repaired