hybrid picking

When hybrid picking 2 notes at the same time, I'm struggling to to get the note plucked to ring at the same volume as the note picked with the plectrum. The picked note is always louder than the plucked one.

Any suggestions

This is usually picking dynamics issue.  Often we pick much harder than we need to & it's wasted effort because at a certain point the string is only going to be so loud & playing harder just creates tension.  Tension decreases endurance & makes it harder to get to the next note on time. 

I would start by just working on developing a lighter picking technique.  As you work on picking lighter throw in some hybrid fingerpicking and try to match that lower dynamic with your picking attack. 

If your picking is already light & the problem is your hybrid picking, then you'll have to focus on isolating that element & getting it loud enough.  Keep in mind the same principle applies.  Stay relaxed, light attack, efficiency of motion.  Gradually add in the pick to match volume and attack.

Anders covers hybrid picking on electric here.

https://www.guitartricks.com/lesson/28133

And acoustic here.

https://www.guitartricks.com/lesson/29780

Hope that helps.  Please ask more if necessary.