documentclass[12pt]{article}
usepackage[utf8]{inputenc}
usepackage{amsmath,amssymb}
usepackage{graphicx,tikz,tikz-cd}
usepackage[margin=2.25cm]{geometry}
usepackage{fancyhdr}
pagestyle{fancy}
lhead{Tikz vs. Tikz-cd}
cfoot{}
begin{document}
I have done this using just Tikz in the past.
[begin{tikzpicture}[node distance=2cm]
    node (Q1){$0$};
    node[right of=Q1] (Q2){$L$};
    node[right of=Q2] (Q3){$M$};
    node[right of=Q3] (Q4){$N$};
    node[right of=Q4] (Q5){$0$};
    draw[->,thick] (Q1) -- (Q2);
    draw[->,thick] (Q2) -- node[pos=.5,above]{$psi$}(Q3);
    draw[->,thick] (Q3) -- node[pos=.5,above]{$varphi$}(Q4);
    draw[->,thick] (Q4) --(Q5);
    draw [bend left,->,dashed] (Q4) to node[pos=.5,below]{$alpha$}(Q3);
    draw [bend left,->,dashed] (Q3) to node[pos=.5,below left]{$beta$}(Q2);
end{tikzpicture}]

Now I am trying to switch to using Tikz-cd, and I would like to add a curved under arrow from the zero on one end to the other. I have been able to solve the rest of it but I am not very fluent with the tikz-cd syntax yet.

[begin{tikzcd}[node distance=2cm]
   0 arrow[mapsto]{r}{varphi^{(1)}_{1}}
& 24 arrow[mapsto]{r}{varphi^{(1)}_{1}}
& 17 arrow[mapsto]{r}{varphi^{(1)}_{1}}
& 18 arrow[mapsto]{r}{varphi^{(1)}_{1}}
& 0
end{tikzcd}]

& 0 arrow[mapsto, bend left]{l}

documentclass[a4paper,12pt]{article}

usepackage{tikz-cd,amsmath,amssymb}

begin{document}
begin{tikzcd}
0 arrow[r, "varphi^{(1)}_{1}", maps to] & 24 arrow[r, "varphi^{(1)}_{1}", maps to] & 17 arrow[r, "varphi^{(1)}_{1}", maps to] & 18 arrow[r, "varphi^{(1)}_{1}", maps to] & 0 arrow[llll, maps to, bend left]
end{tikzcd}
end{document}