Solve in the set of real numbers:
\[ 3\left(x^2 \plus{} y^2 \plus{} z^2\right) \equal{} 1,
\]

\[ x^2y^2 \plus{} y^2z^2 \plus{} z^2x^2 \equal{} xyz\left(x \plus{} y \plus{} z\right)^3.
\]
1. **Identify the given equations:**
   \[
   3(x^2 + y^2 + z^2) = 1
   \]
   \[
   x^2y^2 + y^2z^2 + z^2x^2 = xyz(x + y + z)^3
   \]

2. **Check for simple solutions:**
   - Let's test \( (0, 0, \pm \frac{1}{\sqrt{3}}) \):
     \[
     3\left(0^2 + 0^2 + \left(\pm \frac{1}{\sqrt{3}}\right)^2\right) = 3 \left( \frac{1}{3} \right) = 1
     \]
     \[
     0^2 \cdot 0^2 + 0^2 \cdot \left(\pm \frac{1}{\sqrt{3}}\right)^2 + \left(\pm \frac{1}{\sqrt{3}}\right)^2 \cdot 0^2 = 0
     \]
     \[
     0 \cdot (0 + 0 + \pm \frac{1}{\sqrt{3}})^3 = 0
     \]
     Both equations are satisfied, so \( (0, 0, \pm \frac{1}{\sqrt{3}}) \) are solutions.

3. **Use AM-GM inequality and triangle inequality:**
   - Consider the absolute values:
     \[
     |xyz(x + y + z)^3| = |x^2y^2 + y^2z^2 + z^2x^2|
     \]
     \[
     |xyz| |(x + y + z)^3| = x^2y^2 + y^2z^2 + z^2x^2
     \]
     \[
     |xyz| |(x + y + z)^3| \geq |xyz| (|x| + |y| + |z|)
     \]
     \[
     |xyz| |(x + y + z)^3| \geq |xyz| |x + y + z|
     \]
     \[
     |xyz| |x + y + z| ((x + y + z)^2 - 1) \geq 0
     \]

4. **Analyze the case \( xyz(x + y + z) = 0 \):**
   - If \( xyz(x + y + z) = 0 \), then at least one of \( x, y, z \) must be zero.
   - If two of \( x, y, z \) are zero, then the remaining variable must satisfy:
     \[
     3z^2 = 1 \implies z = \pm \frac{1}{\sqrt{3}}
     \]
     This gives the solutions \( (0, 0, \pm \frac{1}{\sqrt{3}}) \).

5. **Analyze the case \( (x + y + z)^2 \geq 1 \):**
   - If \( (x + y + z)^2 \geq 1 \), then:
     \[
     xy + yz + zx \geq \frac{1}{3} = x^2 + y^2 + z^2 \geq xy + yz + zx
     \]
     - From the equality case of the trivial inequality, we get \( x = y = z \).
     - Substitute \( x = y = z \) into the first equation:
       \[
       3(3x^2) = 1 \implies 9x^2 = 1 \implies x^2 = \frac{1}{9} \implies x = \pm \frac{1}{3}
       \]
     - This gives the solutions \( \left( \pm \frac{1}{3}, \pm \frac{1}{3}, \pm \frac{1}{3} \right) \).

6. **Conclusion:**
   - The solutions are \( (0, 0, \pm \frac{1}{\sqrt{3}}) \) and \( \left( \pm \frac{1}{3}, \pm \frac{1}{3}, \pm \frac{1}{3} \right) \), including permutations.

The final answer is \( \boxed{ (0, 0, \pm \frac{1}{\sqrt{3}}) } \) and \( \left( \pm \frac{1}{3}, \pm \frac{1}{3}, \pm \frac{1}{3} \right) \).