Simulation doubt with Zener diode & MOSFET
1-
From your simulation, I can see that you decided to use wrong MOSFET parameter.
\$V_T = 1.5V\$ and \$\beta = 20 \text{m}\:A/V^2 \$
And this, for example, will give us the drain current for \$V_{GS} = 4.5V\$ equal to:
$$I_D = \frac{\beta}{2}(V_{GS} - V_T)^2 = 90 \text{mA} $$
Therefore you need to increase the \$\beta\$ value.
We can calculate the needed \$\beta\$ value by using this approximate equation (MOSFET in Triode region)
$$\beta = \frac{1}{R_{DS(ON)}(V_{GS} - V_T)}$$
For example for \$V_T = 1.5V\$, \$V_{GS} = 10V\$,\$ R_{DS(ON)} = 30\text{m}\Omega \$
$$\beta = \frac{1}{R_{DS(ON)}(V_{GS} - V_T)} = \frac{1}{30\text{m}\Omega(10V - 1.5V)} \approx 4 \:A/V^2$$
Thus to fix your simulation you need to increase the \$\beta\$ value.

When I apply a negative voltage of -14V to the gate of the bottom
MOSFET as shown below, I get a voltage at the Zener cathode as 2.195
and a voltage between the MOSFET nodes as 2.7V with 6.4mA of current?
Can someone tell me how this 2.195V and 2.7V is appearing? Just want
to understand the circuit behaviour in these conditions. Please help.

Hmm...strange circuit.
The upper MOSFET will be ON because the gate of the upper MOSFET is at \$+5V\$.
So the current will continue to flow through the forward-biased Zener diode and into the lower MOSFET gate resistor. And if the MOSFET threshold voltage is low (as is in your case) the lower MOSFET will also be ON.
We can apply KVL here and see what we get:



simulate this circuit &ndash; Schematic created using CircuitLab
$$V_G=V_{GS1}+V_D+V_{GS2}$$
And in your simulation, we have perfectly matched MOSFET's (Id1 = Id2 ignoring diode current, thus Vgs1 = Vgs2 )
$$V_{GS} = \frac{V_G - V_D}{2} = \frac{5V - 0.6V}{2} = 2.2V$$
And the voltage at the \$T_2\$ drain will be \$V_{D2} = V_{GS}+V_D = 2.8V\$
\$I_{D2} = \frac{\beta}{2}(V_{GS} - V_T)^2 = \frac{20\text{m}}{2}(2.2V - 1.5V)^2 = 4.9\text{mA}\$
\$I_{D1} = I_{D2} + I_{DZ} = 4.9\text{mA} + \frac{2.2V+14V}{10k\Omega} = 6.5\text{mA}\$
And I must say that I don't like this circuit at all.
Why the Zener diode is connected between the gate and the drain of a lower MOSFET?