For undirected graphs, Theorem 2.2 in this paper might help a bit.

UPDT: Let $G$ be a weighted undirected graph with Laplacian matrix $L$. Let $D$ be a positive diagonal matrix. Let $d=min(diag(D))$ and let $\Delta$ be the maximum diagonal entry of $L$. Let $i$ be the weighted isoperimetric number of $G$. Then: $$ \lambda_{2}(DL) \geq d (\Delta-\sqrt{\Delta^{2}-i^{2}}) $$

For undirected graphs, Theorem 2.2 in this paper might help a bit.

UPDT: Let $G$ be a weighted undirected graph with Laplacian matrix $L$. Let $D$ be a positive diagonal matrix. Let $d=\min(\operatorname{diag}(D))$ and let $\Delta$ be the maximum diagonal entry of $L$. Let $i$ be the weighted isoperimetric number of $G$. Then: $$ \lambda_{2}(DL) \geq d \left(\Delta-\sqrt{\Delta^{2}-i^{2}}\right) $$

For undirected graphs, Theorem 2.2 in this paper might help a bit.

For undirected graphs, Theorem 2.2 in this paper might help a bit.

UPDT: Let $G$ be a weighted undirected graph with Laplacian matrix $L$. Let $D$ be a positive diagonal matrix. Let $d=min(diag(D))$ and let $\Delta$ be the maximum diagonal entry of $L$. Let $i$ be the weighted isoperimetric number of $G$. Then: $$ \lambda_{2}(DL) \geq d (\Delta-\sqrt{\Delta^{2}-i^{2}}) $$