I have a model with lots of variables indexed over a few sets.

After having introduced the model, i.e. having already said that $x_{zt}$ has indexes $z\in Z$ and $t\in T$, instead of writing

"we consider the variables $x_{zt}$..."

or

" we consider the variables $x_{zt}$, with $z\in Z,\\, t\in T$"

I tend to use

" we consider the variables $\{x_{zt}\}_{Z\times T}$"

I know the indexes are usually repeated in the subscript, e.g. it should be $\{x_{zt}\}_{(z,t)\in Z\times T}$, but I saw this done only when there was a single index; furthermore it would take longer to write and would be hard to read.

I think the notation I'm using is a good compromise, would you agree?

TIA