Does de EUR/USD cotization affect the profit?

Hi, sorry for such a dumb question but i have to do it.
Im from EU so i live in EUR (final exchange is EUR, i pay the power in EUR, etc)
I always see all altcoins exchanges based on USD (btc/usd, zec/usd, etc)

Now (to me) the usd are really cheap and im afraid of losing profit.

How the exchange of zec to EUR its calculated? The calculate directly to eur or based on usd?
I mean, lets say the eur/usd pair is 1,25$/€ and zec/usd its 500$/zec it would be calculated 500/1,25=400€/zec or it have their own exchange?

This is reall important for me. I need to know if i have to trade all in usd waiting usd to recover.

Ty in advance.

my speculations is that USD is not going to recover , its going into the abyss .
in 2 years time I expect EUR = 1.5 USD maybe more .

and your calculation is right
1zec now for example = 400 usd

thats 400/1.25=320 EUR .

Roger that.

Ty for your help.