The general answer to “Is it ok to cross-post between Stack Exchange sites?” is no. However, cross-posts between sites in different languages are different: in the end, a question asked and answered on multiple English sites doesn't help more people than if the question had been asked and answered on a single site, whereas a question asked and answered in two languages helps more people.

So rather than the general rule, I would apply something closer to the case of cross-posting between distinct sites. It's ok to do it, but:

1. Mention it explicitly, and link the questions to each other.
2. If you get a good answer on one side which doesn't have an equivalent on the other side, then copy the answer over — that is, post a translation of the other-language answer, with proper attribution.

The general answer to “Is it ok to cross-post between Stack Exchange sites?” is no. However, cross-posts between sites in different languages are different: in the end, a question asked and answered on multiple English sites doesn't help more people than if the question had been asked and answered on a single site, whereas a question asked and answered in two languages helps more people.

So rather than the general rule, I would apply something closer to the case of cross-posting between distinct sites. It's ok to do it, but:

1. Mention it explicitly, and link the questions to each other.
2. If you get a good answer on one side which doesn't have an equivalent on the other side, then copy the answer over — that is, post a translation of the other-language answer, with proper attribution.

The general answer to “Is it ok to cross-post between Stack Exchange sites?” is no. However, cross-posts between sites in different languages are different: in the end, a question asked and answered on multiple English sites doesn't help more people than if the question had been asked and answered on a single site, whereas a question asked and answered in two languages helps more people.

So rather than the general rule, I would apply something closer to the case of cross-posting between distinct sites. It's ok to do it, but:

1. Mention it explicitly, and link the questions to each other.
2. If you get a good answer on one side which doesn't have an equivalent on the other side, then copy the answer over — that is, post a translation of the other-language answer, with proper attribution.

The general answer to “Is it ok to cross-post between Stack Exchange sites?” is no. However, cross-posts between sites in different languages are different: in the end, a question asked and answered on multiple English sites doesn't help more people than if the question had been asked and answered on a single site, whereas a question asked and answered in two languages helps more people.

So rather than the general rule, I would apply something closer to the case of cross-posting between distinct sites. It's ok to do it, but:

1. Mention it explicitly, and link the questions to each other.
2. If you get a good answer on one side which doesn't have an equivalent on the other side, then copy the answer over — that is, post a translation of the other-language answer, with proper attribution.