How to output 24V for two 12V isolation transformers?

There are two isolation transformers with output of 12V. Can we get 24V output voltage through these two transformers? How can we achieve this?

In fact, if the input voltage of the transformer is the same, it can be connected in parallel with each other. If the input voltage is not the same, the original transformer cannot be spliced.

For example, if two 220V to 12V isolation transformers are connected in parallel with the input and output ends (220V) of the transformer; if one end of the 12V output end of one transformer is connected (in series) with the other end of the 12V output end of the transformer, 24V output voltage can be obtained.

It is worth mentioning that this approach is only used in informal places or in emergencies, because there are many disadvantages: