My point is, even without rushing you can comfortably see all birds in 6-7 or max. 8 weeks, but you need to visit the right sites (i.e. Bemenavika, Ankarafantsika, Betsiboka delta + lake kinkony, Masoala, Andohahela, Ranomafana, Berenty, Ifaty, Tulear, Zombitse, Isalo, Anjozorobe)
No need to visit Anjozorobe if you can find Slender-billed Flufftail in Bemenavika, and no need to visit Mantadia-Perinet and surroundings if you have visited the sites mentioned above. Each sites takes approx. 2 days of birding and less than 10 target species.
A 4x4 + internal flights would take you around in 4 weeks covering all the sites, travelling overland with public transport and you spend 6-7 weeks, or 8 if you go really slow.
The very best sites I have experienced were Bemenavika and Masoala. I haven't birded in the south but friends have and they got most good birds in Ranomafana, and in total all endemics bar Dusky Greenbul (still no hard evidence seen this bird exists, e.g. DNA etc?) and a vague claim of the Serpent-eagle (maybe there is now a tagged one in Bemenavika, definitely the best place in Madagascar to try, and has been seen this year by Dutch birder Johannes Fischer:
http://www.dutchbirding.nl/content/news/images/Fischer_serpenteagle.JPG