Help with zoom camera

Hi!! I´m trying to implement a zoom camera using the mouse, and glulookat. Here is my code:

float eyesx = 0.0, eyesy = 0.0, eyesz = 20.0, zoom = 0.01, lasty;
void mouse(int button, int state, int x, int y)
{
	float direccion = 1;
	float ydelta = lasty - y;
	if(ydelta>0){
		direccion*=-1;
	}else{
		direccion*=1;
	}
    if (button == GLUT_LEFT_BUTTON) {
        if (state == GLUT_DOWN) {
			lasty = y;
			if(direccion>0){
				//eyesx+=eyesx*zoom;
				//eyesy+=eyesy*zoom;
				eyesz+=eyesz*zoom;
			}else{
				//eyesx-=eyesx*zoom;
				//eyesy-=eyesy*zoom;
				eyesz-=eyesz*zoom;
			}
        } else {
			lasty = y;
        }
    }
	glutPostRedisplay();
}

void display(void)
{
	gluLookAt (eyesx, eyesy, eyesz, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
	printf("eyesx, eyesy, eyesz: %f %f %f 
", eyesx, eyesy, eyesz);
	drawCube();
	glutSwapBuffers();
}

When I run it, no mather what I do, even tough eyesz increases or diminishes; the scene still zooms out.
Some help is welcomed!!

As it stands, the code appears to be repeatedly multiplying gluLookAt matrices. Whenever you call gluLookAt, the previous value of MODELVIEW is replaced with MODELVIEW*M_gluLookAt. You usually set the MODELVIEW matrix to identity then call gluLookAt, only then do you begin drawing your scene… try adding the two lines before gluLookAt:

void display(void)
{
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
	gluLookAt (eyesx, eyesy, eyesz, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

	printf("eyesx, eyesy, eyesz: %f %f %f 
", eyesx, eyesy, eyesz);

        glPushMatrix();
        //glTranslate/glScale/glRotate etc to locate the cube
	drawCube();
        glPopMatrix();
	glutSwapBuffers();
}

And to draw a set of object you usually put each object in a push/pop pair.

Thanks!! It work ok!
But now my pan functions that previously worked, are not working anymore. I hope you can help me. Here is my code where I integrate pan and zoom:

void display(void)
{
	glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
	gluLookAt (eyesx, eyesy, eyesz, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
	printf("eyesx, eyesy, eyesz: %f %f %f 
", eyesx, eyesy, eyesz);
	glPushMatrix();
		dibujarSuperficie();
	glPopMatrix();
	glutSwapBuffers();
}

void mouse(int button, int state, int x, int y)
{
	float direccion1 = 1;
	float ydelta = lasty - y;
	if(ydelta>0){
		direccion1*=-1;
	}else{
		direccion1*=1;
	}
    if (button == GLUT_LEFT_BUTTON) {
        if (state == GLUT_DOWN) {
			lasty = y;
			if(direccion1>0){
				eyesx+=eyesx*zoom;
				eyesy+=eyesy*zoom;
				eyesz+=eyesz*zoom;
			}else{
				eyesx-=eyesx*zoom;
				eyesy-=eyesy*zoom;
				eyesz-=eyesz*zoom;
			}
        } else {
			lasty = y;
			lastx = x;
        }
    }
	else if (button == GLUT_RIGHT_BUTTON) {
        if (state == GLUT_DOWN) {
			lasty = y;
			glRotatef(lastx - x, 0, 0, 1);
			lastx = x;
			glRotatef(lasty - y, 0, 1, 0);
			lasty = y;
        } else {
			lasty = y;
			lastx = x;
        }
    }
	glutPostRedisplay();
}

This is my original code, where the pan worked:

void display(void)
{
	glPushMatrix();
		gluLookAt (0, 0, 20, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
	glPopMatrix();
	//printf("eyesx, eyesy, eyesz: %f %f %f 
", eyesx, eyesy, eyesz);
	glPushMatrix();
		dibujarSuperficie();
	glPopMatrix();
	glutSwapBuffers();
}

void motion(int x, int y)
{
	float xrotrad, yrotrad;
    if (downL) {
		glRotatef(lastx - x, 0, 0, 1);
		lastx = x;
		glRotatef(lasty - y, 0, 1, 0);
		lasty = y;
        glutPostRedisplay();
    }
}

/* ARGSUSED3 */
void mouse(int button, int state, int x, int y)
{
    if (button == GLUT_LEFT_BUTTON) {
        if (state == GLUT_DOWN) {
            lastx = x;
		    lasty = y;
            downL = 1;
        } else {
            downL = 0;
        }
    }
}

What am I doing wrong here?

You may get some benefit looking at GltZPR. The source is a single C-file that you could look at to get some ideas or just use.