if you go to

system audio settings,
device properties, and then,
additional device properties,
then the 'Advanced' tab there,

you may see something like "Allow applications to take exclusive control of this device".

Unchecking that checkbox might make possible what you want to do.

can't play youtube or zoom when pianoteq is working
How can I solve this one?

Thank you

Are you using Windows?
Then for sure you are using an ASIO driver?

Some ASIO drivers require exclusive access to the audio interface (for example the generic driver ASIO4ALL)...
Therefore if the ASIO driver is active, you have no sound from other applications...

If there are ASIO drivers for your audio interface from the manufacturer, then use them! Avoid ASIO4ALL!
If there are not, you could try "windows audio" as audio device type. But this may lead to latency issues.

Your best option is to get an audio interface with good ASIO drivers

For example I'm using the "NI Komplete Audio 6" audio interface (the old one, silver colored... but I'm sure the new (black colored) is also great).
The ASIO drivers for this device are working great, I still have sound from Youtube or Winamp when using VSTs.
I'm pretty sure, that Focusrite, Steinberg and some other also provide good ASIO drivers.

Thank you