Sex should be as easy as drinking a glass of water. That's Kollontai. I'm unsure about Zalkind's commandments.

Here are the 12 commandments:

1. Sexual life shall not develop too early among the proletariat.

2. Thou shalt exercise sexual restraint until marriage, and marriage shall take place only upon full social and biological maturity (20-25 years).

3. Sexual relations shall be the culmination of a deep and comprehensive sympathy and attachment to the object of thy sexual love.

4. The sexual act shall be the final link in a chain of deep and complex experiences binding the lovers together at that moment.

5. The sexual act shall not be repeated often.

6. Thou shalt not often change thy sexual object. There shall be less sexual variation.

7. Love shall be monogamous and monoandrous (one wife, one husband).

8. Every sexual act must be committed without forgetting the possibility of conceiving a child – thou shalt always remember thy progeny.

9. Sexual selection shall always be conducted along the lines of revolutionary-proletarian class objectives. Elements of flirtation, skirt-chasing, coquetry, and other particular methods of sexual conquest must not be introduced into love relations.

10. Thou shalt not be jealous.

11. Thou shalt not engage in sexual perversions.

12. In the interest of revolutionary expedience, class shall have the right to interfere in the sexual life of its co-members; the sexual shall always be subordinate to class interests, never interfering with the latter, but shall always serve it.

For what it's worth, Lenin calls the "Glass of Water" theory "completely un-Marxist": https://www.marxists.org/archive/zetkin/1920/lenin/zetkin1.htm

I think he comes off as a bit of a prude in this. Maybe Kollontai sometimes goes a little too far but on the whole I think she has a much more progressive position on the topic of sex than Lenin does.