i managed to do it with the following setup:
10x soldier
1x tank/laser cannon
10x laser rifle
10x stun rod
i got a battleship first with mutons. after a somewhat long battle, i ended up with several live mutons, all soldiers/navigators/engineers, but no leader or commander. the next one was an ethereal one, i managed to neutralize 2 leaders and a commander, lost 3 rookies. it was at the beginning of october, 1999.
i tried cydonia first at the middle of february, 2000, and i was successful, but got most of my crew killed.
next time i had 10 rookies screened with 85+ psi strength and some skill, too, all in power armor, with a single blaster launcher and 12 bombs for it, and 10 psi-amps. this time it was a great experience, without losses.
i made 8 plasma beams, one for each interceptor on every base. other interceptors were present with dual avalanches.
all of these were funded by manufacturing of motion scanners, then laser cannons globally.
the save/load function was extremely heavily used throughout the game.
end result:
victory, 1st aug 2000
difficulty: beginner
average monthly rating: 466
total income: $9 434 725 675
total expenditure: $9 083 686 452
missions accomplished: 2
missions failed: 0
night missions: 0
best mission rating: 1795
worst mission rating: 851
soldiers recruited: 18
soldiers lost: 3
aliens killed: 8
aliens captured: 2
friendly fire incidents: 0
average accuracy: 3%
most effective weapon: psi-amp
deadliest alien: ethereal
longest months in service: 10
sick days: 0
ufos detected: 610
alien bases discovered: 14
countries infiltrated: 5
terror attacks: 6
bases built: 8
craft owned: 22
scientists hired: 0
engineers hired: 1710
research completed: 46
"missions accomplished" should possibly show 3, for cydonia is made up of two.
"night missions" should read 1, because the first part of the cydonia mission goes always at night (but why?).
soldiers, engineers and scientists shown here are counted at the beginning of the final mission. of course i had 200 scientists once, but sacked them after finishing the research. at least 1000 more engineers got sacked/lost.
"aliens killed": it seems that the cydonian kills are not included here.
"aliens captured": the first part of mars was finished by mind-controlling the last sectoid. somehow the 2 leaders and 1 commander i stunned on my only ufo recovery mission ended up as a "2" here.
"bases built" is also inaccurate, because i lost 6 bases to retaliation attacks. of course at the launch of the cydonia mission, there were 8. i would appreciate a "bases lost" entry here.
"craft owned": not accurate either. although i did not lose any, i sacked my skyranger two times.