3D orienting particles using velocity and position vectors in p5js

I'm currently writting a 3D implementation of the boids algorithm in P5.js but I'm having trouble orienting my boids according to their direction (velocity). Rotations are limited to RotateX(), RotateY() and RotateZ(). The simplest solution that I feel should work goes along these lines :

push();

translate(this.pos); 
rotateZ(createVector(this.vel.x, this.vel.y).heading());
rotateY(createVector(this.vel.x, this.vel.z).heading());

beginShape();
// Draw Boid Vertices..
endShape();

pop();

But it doesn't.

I've written a much smaller version of the program which contains only the orientation for randomly generated particles that go in a single direction. It is available here directly on the p5js website : https://editor.p5js.org/itsKaspar/sketches/JvypSPGGh There is a default orbit control so you can zoom and drag the mouse to check the orientation of the particles.

Thanks so much, I've been stuck on this for half a day now

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